Sculpted silicon for epitaxial digit line growth in vertical three-dimensional (3D) memory

Abstract

Systems, methods and apparatus are provided for an array of vertically stacked memory cells having horizontally oriented access devices and storage nodes. The horizontally oriented access devices having a first source / drain regions and a second source / drain regions separated by channel regions. Gates at the channel regions formed fully around every surface of the channel region as gate-all-around (GAA) structures separated from channel regions by gate dielectrics. The memory cells have horizontally oriented storage nodes connected to the second source / drain regions and digit lines connected to the first source / drain regions.

Description

SCULPTED SILICON FOR EPITAXIAL DIGIT LINE GROWTH IN VERTICAL THREE-DIMENSIONAL (3D) MEMORYTECHNICAL FIELD

[0001] The present disclosure relates generally to memory devices, and more particularly, to sculpted silicon for epitaxial digit line growth in vertical three-dimensional (3D) memory.BACKGROUND

[0002] Memory' is often implemented in electronic systems, such as computers, cell phones, hand-held devices, etc. There are many different types of memory, including volatile and non-volatile memory. Volatile memory may require power to maintain its data and may include random-access memory (RAM), dynamic random-access memory (DRAM), static random-access memory (SRAM), and synchronous dynamic random-access memory (SDRAM). Non-volatile memory may provide persistent data by retaining stored data when not powered and may include NAND flash memory', NOR flash memory', nitride read only memory (NROM), phase-change memory (e.g., phase-change random access memory ), resistive memory' (e.g., resistive randomaccess memory), cross-point memory’, ferroelectric random-access memory (FeRAM), or the like.

[0003] As design rules shrink, less semiconductor space is available to fabricate memory', including DRAM arrays. A respective memory' cell for DRAM may include an access device, e.g.. transistor, having a first and a second source / drain regions separated by epitaxially grown channel regions. A gate may oppose the channel region and be separated therefrom by a gate dielectric. An access line, such as a word line, is electrically connected to the gate of the DRAM cell. A DRAM cell can include a storage node, such as a capacitor cell, connected by the access device to a digit line. The access device can be activated (e.g., to select the cell) by an access line connected to the access transistor. The capacitor can store a charge corresponding to a data value of a respective cell (e.g., a logic “1” or “0”).BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 A is a schematic illustration of a horizontal access device in a vertical three-dimensional (3D) memory in accordance a number of embodiments of the present disclosure.

[0005] Figure 1 B is a perspective view illustrating a portion of a horizontal access device in vertical three-dimensional (3D) memon' in accordance with a number of embodiments of the present disclosure.

[0006] Figure 2 illustrates a portion of a horizontal access device in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure.

[0007] Figure 3 illustrates a portion of a vertical 3D memon' array in accordance with a number of embodiments of the present disclosure.

[0008] Figure 4 is a cross-sectional view, at one stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure.

[0009] Figures 5A to 5B illustrate an example method, at one stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0010] Figures 6A to 6C illustrate an example method, at another stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0011] Figures 7A to 7C illustrate an example method, at another stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0012] Figures 8A to 8C illustrate an example method, at another stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0013] Figures 9A to 9C illustrate a first example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0014] Figures 10A to IOC illustrate a second example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0015] Figures 11 A to 11C illustrate a third example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0016] Figures 12A to 12D illustrate a method, at another stage of a semiconductor fabrication process, for epitaxially growing Si material along particular crystalline plane orientations for epitaxial digit line grow th in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0017] Figures 13A to 13B illustrate an example method, at another stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory, in accordance with a number of embodiments of the present disclosure.

[0018] Figure 14 is a block diagram of an apparatus in the form of a computing system including a memory device in accordance with a number of embodiments of the present disclosure.DETAILED DESCRIPTION

[0019] Embodiments of the present disclosure describe epitaxial digit line grow th in vertical three-dimensional (3D) memory. A vertically oriented digit line is formed with horizontally oriented access devices and access lines in an array of vertically stacked memory cells. The horizontal access devices are integrated with horizontally oriented access lines having a first source / drain regions and a second source / drain regions separated by channel regions and integrated with vertically oriented digit lines. In vertically stacked memoryarray structures, such as transistor structures, polycrystalline silicon (also referred to as polysilicon) can be leaky, allowing current to leak through the poly crystalline structure, making the transistor less effective. Single crystal silicon is not very leaky. However, single crystal silicon cannot grow on amorphous dielectric materials, such as oxides or nitrides, which are the common materials upon which transistors are formed.

[0020] However, as disclosed in the embodiments of the present disclosure, it is possible to use a silicon wafer for a transistor that can be utilized as a substrate during the high temperature processes required for single crystal silicon formation. In such embodiments, a layer of silicon germanium can be grown on the silicon substrate. Single crystal silicon can, then, be grown on the silicon germanium.

[0021] This may be accomplished, for example, by providing a thin single crystal silicon germanium layer, as a seed layer, and then forming the single crystal silicon germanium layer thickness. Once the desired layer thickness is formed, a silicon layer can be formed into the surface of the silicon germanium layer. As with the silicon germanium layer, this may be accomplished, for example, by providing a thin single crystal silicon layer, as a seed layer, and then forming the thin single crystal silicon layer thickness into a thicker single crystal silicon layer.

[0022] Depending on the silicon germanium concentration, if silicon is x quantity and germanium is y quantity’ and, if y is smaller than x, then silicon / silicon germanium has a small lattice mismatch with respect to the lattice of single crystal silicon. This allows silicon to be formed on top of silicon germanium with a single crystal structure. If a thin layer of single crystal silicon is applied to the surface of the silicon germanium, then the whole silicon layer acts as a seed for the growth of the single cry stal silicon layer. Such layering can be done in alternating iterations (e.g., SiGe / Si / SiGe / Si, etc.) to create a superlattice structure in the form of a vertical stack such as shown in Figure 4.

[0023] For example, a seed layer of silicon germanium can be formed that is 100 Angstroms in thickness (height) and can be grown to, for example 1000 Angstroms. A thin silicon seed layer can be formed on the surface of the silicon germanium layer that is, for example. 50 Angstroms and can be grown to a thickness of, for example, 300 Angstroms. These thicknesses are merelyprovided as examples and should not be regarded as limiting unless recited explicitly in a particular claim.

[0024] The transistor devices of the present disclosure will have better performance with regard to I-on, better I-off, drivability, and / or leakage current because there is no grain boundary and therefore current cannot leak through the grain boundary which is where leakage often occurs in polysilicon. In some embodiments, devices can have, for example, three orders of magnitude lower I- off (leakage).

[0025] Advantages to the structure and process described herein can include a lower off-current (loff) for the access devices, as compared to silicon based (Si-based) access devices (e.g., transistors), better DRAM refresh requirement, and / or reduced gate / drain induced leakage (GIDL) for the access devices. Combined with a gate all around (GAA) structure at the channel region of the semiconductor material, provides better electrostatic control on the channel, better subthreshold slope and a more cost-effective process.

[0026] During formation of the 3D memory array, one step in the semiconductor fabrication process can include forming digit lines. In the process described herein, the digit lines can be vertically oriented in the 3D memory array. The digit lines can be formed in a vertical opening in the 3D memory array to conductively interconnect memory cells along vertical columns.

[0027] In some examples, the vertical columns are high aspect ratio spaces. Therefore, epitaxially growing the vertically oriented digit lines within the vertical column can ensure that the digit lines extend the full depth of the vertical columns and continuously touch every Si channel in the vertical columns.

[0028] However, epitaxial growth of Si material can occur both vertically as well as horizontally. Accordingly, a risk of horizontal merging of Si material during epitaxial growth of the vertical digit line is present. If such horizontal merging occurs, laterally adjacent vertically oriented digit lines may be electrically shorted together.

[0029] Epitaxial digit line growth in vertical 3D memory' according to the disclosure can allow for epitaxial growth of vertical digit lines without horizontal merging occurring. Various mechanisms for preventing horizontalmerging of epitaxially grown adjacent vertical digit lines can be utilized in order to prevent laterally adjacent vertically oriented digit lines from being electrically shorted together, as is described herein.

[0030] The figures herein follow a numbering convention in which the first digit or digits correspond to the figure number of the drawing and the remaining digits identify an element or component in the drawing. Similar elements or components between different figures may be identified by the use of similar digits. For example, reference numeral 103 may reference element “03"’ in Figure 1, and a similar element may be referenced as 203 in Figure 2. Multiple analogous elements within one figure may be referenced with a reference numeral followed by a hyphen and another numeral or a letter. For example, 302-1 may reference element 302-1 in Figure 3 and 302-2 may reference element 302-2, which may be analogous to element 302-1. Such analogous elements may be generally referenced without the hyphen and extra numeral or letter. For example, elements 302-1 and 302-2 or other analogous elements may be generally referenced as 302.

[0031] Figure 1 A is a schematic illustration of a horizontal access device in a vertical three-dimensional (3D) memory' in accordance a number of embodiments of the present disclosure. Figure 1 A illustrates a circuit diagram showing a cell array of a 3D semiconductor memory device according to embodiments of the present disclosure. Figure 1 A illustrates that a cell array may have a plurality7of sub cell arrays 101-1, 101-2, . . ., 101-N. The sub cell arrays 101-1, 101-2, . . ., 101-N may be arranged along a second direction (D2) 105. Each of the sub cell arrays, e.g., sub cell array 101-2, may include a plurality' of access lines 107-1, 107-2, . . ., 107-P (which also may be referred to as word lines). Also, each of the sub cell arrays, e.g., sub cell array 101-2, may7include a plurality' of digit lines 103-1, 103-2, . . ., 103-Q (which also may be referred to as bit lines, data lines, or sense lines). In Figure 1 A, the access lines 107-1, 107-2. . . .. 107-P are illustrated extending in a first direction (DI) 109 and the digit lines 103-1, 103-2, . . ., 103-Q are illustrated extending in a third direction (D3) 111. According to embodiments, the first direction (DI) 109 and the second direction (D2) 105 may be considered in a horizontal (“X-Y"’) plane. The third direction (D3) 111 may be considered in a vertical (“Z”) plane. Hence,according to embodiments described herein, the digit lines 103-1, 103-2, . . ., 103-Q are extending in a vertical direction, e.g., third direction (D3) 111.

[0032] A memory cell, e.g., memory cell 110, may include an access device, e.g., access transistor, and a storage node located at an intersection of each access line 107-1, 107-2, . . ., 107-P and each digit line 103-1, 103-2, . . ., 103-Q. Memory cells may be written to. or read from, using the access lines 107-1, 107-2. . . ., 107-P and digit lines 103-1. 103-2, . . ., 103-Q. The access lines 107-1, 107-2, . . ., 107-P may conductively interconnect memory cells along horizontal rows of each sub cell array 101-, 101-2, . . ., 101-N, and the digit lines 103-1, 103-2, . . ., 103-Q may conductively interconnect memory cells along vertical columns of each sub cell array 101 -. 101-2, . . .. 101-N. One memory cell, e.g. 1 10, may be located between one access line, e.g., 107-2, and one digit line, e.g., 103-2. Each memory7cell may be uniquely addressed through a combination of an access line 107-1, 107-2, . . ., 107-P and a digit line 103-1, 103-2, . . ., 103-Q.

[0033] The access lines 107-1, 107-2, . . ., 107-P may be or include conducting patterns (e.g., metal lines) disposed on and spaced apart from a substrate. The access lines 107-1, 107-2, . . ., 107-P may extend in a first direction (DI) 109. The access lines 107-1, 107-2, . . ., 107-P in one sub cell array, e.g., 101-2. may be spaced apart from each other in a vertical direction, e g., in a third direction (D3) 1 1 1.

[0034] The digit lines 103-1, 103-2, . . ., 103-Q may be or include conductive patterns (e.g., metal lines) extending in a vertical direction with respect to the substrate, e.g., in a third direction (D3) 111. The digit lines in one sub cell array, e.g., 101-2, may be spaced apart from each other in the first direction (DI) 109.

[0035] A gate of a memory cell, e.g., memory7cell 110, may be connected to an access line, e.g., 107-2, and a first conductive node, e.g., first source / drain region, of an access device, e.g., transistor, of the memory cell 110 may be connected to a digit line, e.g., 103-2. Each of the memory cells, e.g., memory7cell 110, may be connected to a storage node, e.g., capacitor. A second conductive node, e.g., second source / drain region, of the access device, e.g., transistor, of the memory cell 110 may be connected to the storage node, e.g.. capacitor. While first and second source / drain region references are used hereinto denote two separate and distinct source / drain regions, it is not intended that the source / drain region referred to as the “first” and / or “second” source / drain regions have some unique meaning. It is intended only that one of the source / drain regions is connected to a digit line, e.g., 103-2, and the other may be connected to a storage node.

[0036] Figure IB is a perspective view illustrating a portion of a horizontal access device in vertical three-dimensional (3D) memory, e.g.. a portion of a sub cell array 101-2 shown in Figure 1 A as a vertically oriented stack of memory cells in an array, in accordance with a number of embodiments of the present disclosure.

[0037] As shown in Figure IB. a substrate 100 may have formed thereon one of the plurality of sub cell arrays, e.g., 101-2, described in connection with Figure 1 A. For example, the substrate 100 may be or include a silicon substrate, a germanium substrate, or a silicon-germanium substrate, etc. Embodiments, however, are not limited to these examples.

[0038] As show n in the example embodiment of Figure IB, the substrate 100 may have fabricated thereon a vertically oriented stack of memory cells, e.g., memory cell 110 in Figure 1A, extending in a vertical direction, e.g., third direction (D3) 111. According to some embodiments the vertically oriented stack of memory cells may be fabricated such that each memory cell, e.g.. memory cell 110 in Figure 1 A, is formed on plurality of vertical levels, e.g., a first level (LI), a second level (L2), and a third level (L3). The repeating, vertical levels, LI, L2, and L3, may be arranged, e.g., “stacked”, a vertical direction, e.g., third direction (D3) 111 shown in Figure 1 A. and may be separated from the substrate 100 by an insulator material. Each of the repeating, vertical levels, LI, L2, and L3 may include a plurality of discrete components, e.g., regions, to the horizontally oriented access devices 130, e.g., transistors, and storage nodes, e.g., capacitors, including access line 107-1, 107-2, . . ., 107- P connections and digit line 103-1. 103-2, . . .. 103-Q connections. The plurality of discrete components to the horizontally oriented access devices 130, e.g., transistors, may be formed in a plurality of iterations of vertically, repeating layers within each level, as described in more detail below, and may extend horizontally in the second direction (D2) 105, analogous to second direction (D2) 105 shown in Figure 1 A.

[0039] The plurality of discrete components to the laterally oriented access devices 130. e.g., transistors, may include a first source / drain region 121 and a second source / drain region 123 separated by a channel region 125, extending laterally in the second direction (D2) 105, and formed in a body of the access devices. In some embodiments, the channel region 125 may include silicon, germanium, silicon-germanium, and / or indium gallium zinc oxide (IGZO). In some embodiments, the first and the second source / drain regions. 121 and 123, can include an n-type dopant region formed in a p-type doped body to the access device to form an n-type conductivity7transistor. In some embodiments, the first and the second source / drain regions, 121 and 123, may include a p-type dopant formed within an n-type doped body to the access device to form a p-type conductivity transistor. By way of example, and not by way of limitation, the n-type dopant may include phosphorous (P) atoms and the p-type dopant may include atoms of boron (B) formed in an oppositely doped body region of polysilicon semiconductor material. Embodiments, however, are not limited to these examples.

[0040] The storage node 127, e.g., capacitor, may be connected to one respective end of the access device. As shown in Figure IB, the storage node 127, e.g., capacitor, may be connected to the second source / drain region 123 of the access device. The storage node may be or include memory elements capable of storing data. Each of the storage nodes may be a memory element using one of a capacitor, a magnetic tunnel junction pattern, and / or a variable resistance body which includes a phase change material, etc. Embodiments, however, are not limited to these examples. In some embodiments, the storage node associated with each access device of a unit cell, e.g., memory cell 1 10 in Figure 1 A, may similarly extend in the second direction (D2) 105, analogous to second direction (D2) 105 shown in Figure 1A.

[0041] As shown in Figure IB a plurality of horizontally oriented access lines 107-1. 107-2, . . .. 107-P extend in the first direction (DI) 109. analogous to the first direction (DI) 109 in Figure 1 A. The plurality of horizontally oriented access lines 107-1, 107-2, . . ., 107-P may be analogous to the access lines 107-1, 107-2, . . ., 107-P shown in Figure 1A. The plurality of horizontally oriented access lines 107-1, 107-2, . . ., 107-P may be arranged, e.g., “stacked”, along the third direction (D3) 1 11. The plurality of horizontally oriented access lines 107-1, 107-2, . . 107-P may include a conductive material. For example, the conductive material may include one or more of a doped semiconductor, e.g., doped silicon, doped germanium, etc., a conductive metal nitride, e.g., titanium nitride, tantalum nitride, etc., a metal, e.g., tungsten (W), titanium (Ti), tantalum (Ta), ruthenium (Ru), cobalt (Co), molybdenum (Mo), etc., and / or a metalsemiconductor compound, e.g.. tungsten silicide, cobalt silicide, titanium silicide, etc. Embodiments, however, are not limited to these examples.

[0042] Among each of the vertical levels, (LI), (L2), and (L3), the horizontally oriented memory cells, e.g., memory cell 110 in Figure 1 A, may be spaced apart from one another horizontally in the first direction (DI) 109.However, the plurality of discrete components to the horizontally oriented access devices 130, e.g., first source / drain region 121 and second source / drain region 123 separated by a channel region 125, extending laterally in the second direction (D2) 105, and the plurality7of horizontally oriented access lines 107-1. 107-2, . . ., 107-P extending laterally in the first direction (DI) 109, may be formed within different vertical layers within each level. For example, the plurality7of horizontally oriented access lines 107-1, 107-2, . . ., 107-P, extending in the first direction (DI) 109, may be formed on a top surface opposing and electrically connected to the channel regions 125, separated therefrom by a gate dielectric, and orthogonal to horizontally oriented access devices 130, e.g., transistors, extending in laterally in the second direction (D2) 105. In some embodiments, the plurality7of horizontally oriented access lines 107-1, 107-2, . . ., 107-P, extending in the first direction (DI) 109 are formed in a higher vertical layer, farther from the substrate 100, within a level, e.g., within level (LI), than a layer in which the discrete components, e.g., first source / drain region 121 and second source / drain region 123 separated by' a channel region 125, of the horizontally oriented access device are formed.

[0043] As shown in the example embodiment of Figure IB, the digit lines, 103-1, 103-2. . . ., 103-Q, extend in a vertical direction with respect to the substrate 100, e.g., in a third direction (D3) 11 1. Further, as shown in Figure IB, the digit lines, 103-1, 103-2, . . ., 103-Q, in one sub cell array, e.g., sub cell array 101-2 in Figure 1 A, may be spaced apart from each other in the first direction (DI) 109. The digit lines, 103-1. 103-2, . . .. 103-Q, may be provided, extending vertically relative to the substrate 100 in the third direction (D3) 111 in verticalalignment with source / drain regions to serve as first source / drain regions 121 or, as shown, be vertically adjacent first source / drain regions 121 for each of the horizontally oriented access devices 130, e.g., transistors, extending laterally in the second direction (D2) 105, but adjacent to each other on a level, e.g., first level (LI), in the first direction (DI) 109. Each of the digit lines, 103-1, 103-2, . . ., 103-Q. may vertically extend, in the third direction (D3), on sidewalls, adjacent first source / drain regions 121. of respective ones of the plurality of horizontally oriented access devices 130, e.g., transistors, that are vertically stacked. In some embodiments, the plurality of vertically oriented digit lines 103-1, 103-2, . . ., 103-Q. extending in the third direction (D3) 111, may be connected to side surfaces of the first source / drain regions 121 directly and / or through additional contacts including metal silicides.

[0044] For example, a first one of the vertically extending digit lines, e.g., 103-1, may be adjacent a sidewall of a first source / drain region 121 to a first one of the horizontally oriented access devices 130, e.g., transistors, in the first level (LI), a sidewall of a first source / drain region 121 of a first one of the horizontally oriented access devices 130, e.g., transistors, in the second level (L2), and a sidewall of a first source / drain region 121 a first one of the horizontally oriented access devices 130. e.g., transistors, in the third level (L3), etc. Similarly, a second one of the vertically extending digit lines, e.g., 103-2, may be adjacent a sidewall to a first source / drain region 121 of a second one of the horizontally oriented access devices 130, e.g., transistors, in the first level (LI), spaced apart from the first one of horizontally oriented access devices 130, e.g.. transistors, in the first level (LI) in the first direction (DI) 109. And the second one of the vertically extending digit lines, e.g., 103-2, may be adjacent a sidewall of a first source / drain region 121 of a second one of the laterally oriented access devices 130, e.g., transistors, in the second level (L2), and a sidewall of a first source / drain region 121 of a second one of the horizontally oriented access devices 130, e.g.. transistors, in the third level (L3). etc.Embodiments are not limited to a particular number of levels.

[0045] The vertically extending digit lines, 103-1, 103-2, . . ., 103-Q, may include a conductive material, such as, for example, one of a doped semiconductor material, a conductive metal nitride, metal, and / or a metal-semiconductor compound. The digit lines, 103-1, 103-2, . . ., 103-Q, may correspond to digit lines (DL) described in connection with Figure 1A.

[0046] As shown in the example embodiment of Figure IB, a conductive body contact may be formed extending in the first direction (DI) 109 along an end surface of the horizontally oriented access devices, e.g., transistors, in each level (LI), (L2), and (L3) above the substrate 100. The body contact may be connected to a body e.g.. body region, of the horizontally oriented access devices, e.g., transistors, in each memon cell, e.g., memory cell 1 10 in Figure 1 A. The body contact may include a conductive material such as, for example, one of a doped semiconductor material, a conductive metal nitride, metal, and / or a metal-semiconductor compound.

[0047] Although not shown in Figure IB, an insulating material may fill other spaces in the vertically stacked array of memory cells. For example, the insulating material may include one or more of a silicon oxide material, a silicon nitride material, and / or a silicon oxynitride material, etc. Embodiments, however, are not limited to these examples.

[0048] Figure 2 illustrates a portion of a horizontal access device in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure. Figure 2 illustrates in more detail a unit cell, e.g., memory cell 110 in Figure 1. of the vertically stacked array of memory cells, e g., within a sub cell array 101 -2 in Figure 1 , according to some embodiments of the present disclosure. As show n in Figure 2, the first and the second source / drain regions, 221 and 223, may be impurity' doped regions to the laterally oriented access devices 230. e.g., transistors. The first and the second source / drain regions may be separated by a channel region 225 formed in a body of semiconductor material, e.g., body region of the horizontally oriented access devices 230, e.g., transistors. The first and the second source / drain regions, 221 and 223, may be formed from an n-type or p-type dopant doped in the body region. However, embodiments are not so limited.

[0049] For example, for an n-type conductivity transistor construction the body region of the laterally oriented access devices 230, e.g., transistors, may be formed of a low doped p-type (p-) semiconductor material. In one embodiment, the body region and the channel region 225 separating the first and the second source / drain regions, 221 and 223, may include a low doped, p-type(e.g., low dopant concentration (p-)) polysilicon (Si) material consisting of boron (B) atoms as an impurity dopant to the poly crystalline silicon. The first and the second source / drain regions, 221 and 223, may also comprise a metal, and / or metal composite materials containing ruthenium (Ru), molybdenum (Mo), nickel (Ni), titanium (Ti), copper (Cu), a highly doped degenerate semiconductor material, and / or at least one of indium oxide (In2O3), or indium tin oxide (In2- xSnxO3). formed using an atomic layer deposition process, etc. Embodiments, however, are not limited to these examples. As used herein, a degenerate semiconductor material is intended to mean a semiconductor material, such as poly silicon, containing a high level of doping with significant interaction between dopants, e.g., phosphorus (P), boron (B), etc. Non-degenerate semiconductors, by contrast, contain moderate levels of doping, where the dopant atoms are well separated from each other in the semiconductor host lattice with negligible interaction.

[0050] In this example, the first and the second source / drain regions, 221 and 223, may include a high dopant concentration, n-type conductivity impurity (e.g., high dopant (n+)) doped in the first and the second source / drain regions, 221 and 223. In some embodiments, the high dopant, n-type conductivity' first and second drain regions 221 and 223 may include a high concentration of phosphorus (P) atoms deposited therein. Embodiments, however, are not limited to this example. In other embodiments, the horizontally oriented access devices 230, e.g., transistors, may be of a p-t pe conductivity7construction in which case the impurity, e.g., dopant, conductivity ty pes would be reversed.

[0051] As shown in Figure 2. the first and the second source / drain regions, 221 and 223, may be impurity doped regions to the laterally oriented access devices 230, e.g., transistors. The first and the second source / drain regions may be separated by a channel region 225 formed in a body of semiconductor material, e.g., body region, of the horizontally oriented access devices 230, e.g.. transistors. The first and the second source / drain regions. 221 and 223, may be formed from an n-type or p-type dopant doped in the body region. However, embodiments are not so limited.

[0052] The first source / drain region 221 may occupy an upper portion in the body of the laterally oriented access devices 230, e.g., transistors. For example, the first source / drain region 221 may have a bottom surface within thebody of the horizontally oriented access device 230 which is located higher, vertically in the third direction (D3) 211. than a bottom surface of the body of the laterally, horizontally oriented access device 230. As such, the laterally, horizontally oriented access device 230 may have a body portion which is below the first source / drain region 221 and is in electrical contact with the body contact. Further, as shown in the example embodiment of Figure 2, an access line, e.g., 207, analogous to the access lines 107-1. 107-2, . . .. 107-P shown in Figure 1, may disposed on a top surface opposing and connected to a channel region 225, separated therefrom by a gate dielectric material 204. The gate dielectric material 204 may be, for example, a high-k dielectric material, a silicon oxide material, a silicon nitride material, a silicon oxynitride material, etc., or a combination thereof. Embodiments are not so limited. For example, in high-k dielectric material examples the gate dielectric material 204 may include one or more of hafnium oxide, hafnium silicon oxide, lanthanum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, titanium oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, lithium oxide, aluminum oxide, lead scandium tantalum oxide, lead zinc niobite, etc.

[0053] As shown in the example embodiment of Figure 2, a digit line, e.g.. 203-1, analogous to the digit lines 103-1, 103-2, . . ., 103-Q in Figure 1, may be vertically extending in the third direction (D3) 21 1 adjacent a sidewall of the first source / drain region 221 in the body to the horizontally oriented access devices 230, e.g., transistors horizontally conducting between the first and the second source / drain regions 221 and 223 along the second direction (D2) 205. In this embodiment, the vertically oriented digit line 203-1 is formed symmetrically, in vertical alignment, in electrical contact with the first source / drain region 221. The digit line 203-1 may be formed in contact with an insulator material such that there is no body contact within channel region 225.

[0054] As shown in the example embodiment of Figure 2. the digit line 203-1 may be formed symmetrically within the first source / drain region 221 such that the first source / drain region 221 surrounds the digit line 203-1 all around. The first source / drain region 221 may occupy an upper portion in the body of the laterally oriented access devices 230, e.g., transistors. For example, the first source / drain region 221 may have a bottom surface within the body ofthe horizontally oriented access device 230 which is located higher, vertically in the third direction (D3) 211, than a bottom surface of the body of the laterally, horizontally oriented access device 230. As such, the laterally, horizontally oriented access device 230 may have a body portion which is below the first source / drain region 321 and is in contact with the body contact. An insulator material may fill the body contact such that the first source / drain region 221 may not be in electrical contact with channel region 225. Further, as shown in the example embodiment of Figure 2, an access line, e.g., 207, analogous to the access lines 107-1, 107-2, . . ., 107-P shown in Figure 1, may disposed all around and connected to a channel region 225. separated therefrom by a gate dielectric 204.

[0055] Although the digit line 203-1 is described above as being formed symmetrically within the first source / drain region 221 such that the first source / drain region 221 surrounds the digit line 203-1 all around, embodiments are not so limited. For instance, in some examples, the digit line 203-1 can be formed asymmetrically. In this embodiment, the vertically oriented digit line is formed asymmetrically adjacent in electrical contact with the first source / drain regions 221. The digit line may be formed asymmetrically to reserve room for a body contact in the channel region 225.

[0056] Figure 3 is a perspective view of a memory device in accordance with a number of embodiments of the present disclosure. Figure 3 includes first conductive material 377, an Si material 332, a photolithographic mask material (e g., mask material) 335. an interlayer dielectric (ILD) fill material 367, a second conductive material 370, a metal material 372, a first dielectric material 339, a second dielectric material 333, a second interlayer dielectric material 342, and a plurality of storage nodes (e.g., capacitors) 374.

[0057] Figure 3 illustrates a portion of a vertical 3D memory array that is formed in accordance with the process described in Figures 4-13, as is further described herein. The 3D memory array can include an array of vertically- stacked memory cells having a plurality of levels. Each level of the plurality of levels can include horizontally oriented access devices and storage nodes.

[0058] Each storage node can include horizontally oriented access devices having first source / drain regions and second source / drain regions separated by channel regions, and gates on a gate dielectric material. The arraycan further comprise horizontally oriented access lines forming the gates to the horizontally oriented access devices. The horizontally oriented access lines can be gate all around (GAA) structures. The storage nodes can further include horizontally oriented storage nodes electrically connected to the second source / drain regions of the horizontally oriented access devices.

[0059] The horizontal access devices of the vertical 3D memory array can include the second dielectric material 333. the first dielectric material 377, a first dielectric material 339, and ILD fill material 367. The access devices can be connected to the plurality of storage nodes 374. In some embodiments, the plurality of storage nodes 374 can be double-sided capacitors. The access devices can be used to transfer cunent between the metal material 372 and the plurality of storage nodes 374.

[0060] Further included in the vertical 3D memory array can be epitaxially formed vertical digit lines connected to the first source / drain regions of the horizontally oriented access devices. Devices and methods of forming the epitaxially grown vertical digit lines are further described herein.

[0061] Figure 4 is a cross-sectional view, at one stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory, such as illustrated in Figures 1-3, and in accordance with a number of embodiments of the present disclosure.

[0062] In the example embodiment shown in the example of Figure 4, the method comprises forming alternating layers of a silicon germanium (SiGe) material , 430-1, 430-2, . . ., 430-N (collectively referred to as silicon germanium (SiGe) 430), and a silicon (Si) material, 432-1, 432-2. . . ., 432-N (collectively referred to as epitaxially grown, single crystalline silicon (Si) material 432), in repeating iterations to form a vertical stack 402 on a working surface of a semiconductor substrate 400. In one embodiment, the silicon germanium (SiGe) 430 can be deposited on a dielectric 431 to have a thickness, e.g., vertical height in the third direction (D3), in a range of five (5) nm to thirty (30) nm. In one embodiment, the silicon material 432 can be deposited to have a thickness (t2), e.g., vertical height, in a range of thirty (30) nanometers (nm) to sixty (60) nm. Embodiments, however, are not limited to these examples. As shown in Figure 4, a vertical direction 411 is illustrated as a third direction (D3), e.g., z-directionin an x-y-z coordinate system, analogous to the third direction (D3), among first, second, and third directions, shown in Figures 1-2.

[0063] In some embodiments, the silicon germanium (SiGe), 430-1, 430- 2, . . ., 430-N, may be a mix of silicon and germanium. By way of example, and not by way of limitation, the silicon germanium (SiGe) 430 may be grow n on a dielectric 431 by way of epitaxial growth. Embodiments are not limited to these examples. In some embodiments, the single crystalline silicon (Si) material, 432-1, 432-2, . . ., 432-N, may comprise a silicon (Si) material in a polycrystalline and / or amorphous state. The single crystalline silicon (Si) material, 432-1. 432-2, . . ., 432-N, may be a low7doped, p-type (p-) epitaxially grown, single crystalline silicon (Si) material. The silicon material, 432-1, 432- 2, . . ., 432-N, may also be formed by epitaxially growth on the silicon germanium (SiGe) 430. After the epitaxially grown silicon germanium (SiGe) 430 has been formed, the seed is turned to pure silicon. Embodiments, however, are not limited to these examples.

[0064] The repeating iterations of alternating silicon germanium (SiGe), 430-1, 430-2, . . ., 430-N layers and epitaxially grown, single crystalline silicon (Si) material, 432-1, 432-2, . . ., 432-N layers may be deposited according to a semiconductor fabrication process such as chemical vapor deposition (CVD) in a semiconductor fabrication apparatus. Embodiments, however, are not limited to this example and other suitable semiconductor fabrication techniques may be used to deposit the alternating layers of epitaxially grown silicon germanium (SiGe) and epitaxially grown, single crystalline silicon (Si) material, in repeating iterations to form the vertical stack 402.

[0065] The layers may occur in repeating iterations vertically. In the example of Figure 4, N+l tiers, numbered 1, 2, 3, N, and N+l of the repeating iterations are shown. For example, the stack may include: a first silicon germanium (SiGe) 430-1, a first Si material 432-1. a second SiGe material 430-2. a second Si material 432-2, a third SiGe material 430-3. and a Si material 432-3, in further repeating iterations. Embodiments, however, are not limited to this example and more or few er repeating iterations may be included.

[0066] Figure 5A illustrate an example method, at one stage of a semiconductor fabrication process, for epitaxial digit line growth in verticalthree-dimensional (3D) memory, such as illustrated in Figures 1-3, and in accordance with a number of embodiments of the present disclosure.

[0067] Figure 5 A illustrates a top-down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. In the example embodiment show n in the example of Figure 5A, the method comprises using an etchant process to form a plurality of first vertical openings 515, having a first horizontal direction (DI) 509 and a second horizontal direction (D2) 505, through the vertical stack to the substrate. In one example, as shown in Figure 5A, the plurality of first vertical openings 515 are extending predominantly in the second horizontal direction (D2) 505 and may form elongated vertical, columns 513-1, 513-2. . . ., 513-M (collectively and / or independently referred to as 513), with sidewalls 514 in the vertical stack. The plurality of first vertical openings 500 may be formed using photolithographic techniques to pattern a photolithographic mask 535, e.g., to form a hard mask (HM), on the vertical stack prior to etching the plurality of first vertical openings 515. Similar semiconductor process techniques may be used at other points of the semiconductor fabrication process described herein.

[0068] Figure 5B is a cross sectional view, taken along cut-line A-A’ in Figure 5A, showing another view of the semiconductor structure at a particular time in the semiconductor fabrication process. The cross-sectional view shown in Figure 5B shows the repeating iterations of alternating layers of silicon germanium (SiGe) 530 and silicon (Si) material 532 on a semiconductor substrate 500 to form the vertical stack, e.g. 402 as shown in Figure 4.

[0069] As shown in Figure 5B, a plurality of first vertical openings may be formed through the layers within the vertically stacked memory cells to expose vertical sidewalls in the vertical stack and form elongated vertical columns 513 and then filled with a first dielectric material 539. The vertical openings may be formed through the repeating iterations of the silicon germanium (SiGe) 530 and the silicon (Si) material 532.

[0070] The vertical openings may be formed to expose vertical sidewalls in the vertical stack. The vertical openings may extend in a second horizontal direction (D2) 505 to form the elongated vertical, columns with first vertical sidewalls in the vertical stack and then filled with the dielectric material 539.

[0071] As shown in Figure 5B, a first dielectric material 539, such as an oxide or other suitable spin on dielectric (SOD), may be deposited in the vertical openings, using a process such as CVD, to fill the vertical openings. First dielectric material 539 may also be formed from a silicon nitride (Si3N4) material. In another example, the first dielectric material 539 may include silicon oxy-nitride (SiOxNy). and / or combinations thereof. Embodiments are not limited to these examples. The plurality of first vertical openings may be formed using photolithographic techniques to pattern a photolithographic mask 535, e.g., to form a hard mask (HM), on the vertical stack prior to etching the plurality of first vertical openings. In one embodiment, hard mask 535 may be deposited over silicon germanium (SiGe) 530. Similar semiconductor process techniques may be used at other points of the semiconductor fabrication process described herein.

[0072] Figure 6A illustrates an example method, at another stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure. Figure 6A illustrates a top-down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments.

[0073] In the example embodiment of Figure 6A, the method comprises using a photolithographic process to pattern a photolithographic mask 635. A plurality' of second vertical openings 670 may be formed using the photolithographic mask 635.

[0074] For example, the semiconductor fabrication process can include using an etchant process to form a plurality’ of second vertical openings 670, extending primarily in the first direction (DI) 609 through the vertical stack by patterning and selectively removing the silicon (Si) 632 and silicon germanium (SiGe) 630 material in the plurality of second vertical openings 670 to expose second vertical sidewalls adjacent a first region, e.g., access device region, of the Si and SiGe material 632 and 630.

[0075] The semiconductor fabrication process can further include doping a first source / drain region of the Si material 632. That is, the first Si material 632-1, the second Si material 632-2, the third Si material 632-3. and in further repeating iterations, can be doped. For example, a first source / drain region maybe formed by gas phase doping a dopant into a side surface portion of the Si material 632. In some embodiments, the source / drain region may be a first source / drain region that will connect to a digit line connection. In one example, gas phase doping may be used to achieve a highly isotropic (e.g., non-directional doping), to form the first source / drain regions for the horizontally oriented access devices. In another example, thermal annealing with doping gas, such as phosphorous (P) may be used with a high energy plasma assist to break the bonding. Embodiments, however, are not so limited and other suitable semiconductor fabrication techniques may be utilized.

[0076] Figure 6B illustrates a cross sectional view, taken along cut-line A-A’ in Figure 6A, showing another view of the semiconductor structure at this particular point in one example semiconductor fabrication process of an embodiment of the present disclosure. The cross-sectional view shown in Figure 6B shows the repeating iterations of alternating layers of the silicon germanium (SiGe) 630 and the silicon (Si) material 632, on a semiconductor substrate 600.

[0077] As mentioned in Figure 6A, the semiconductor fabrication process can include forming second vertical openings 670 (e.g., illustrated in Figure 6A) through the layers within the vertically stacked memory cells to expose vertical sidewalls in the vertical stack 402 as shown in Figure 4. The vertical openings 670 can extend predominantly in a first horizontal direction (DI ) 609.

[0078] As shown in Figure 6C, the semiconductor fabrication process can further include selectively etching the silicon germanium (SiGe) 630 isotropically to form a plurality of first horizontal openings in the first region separating layers of the Si material 632. The etching process may be a timed, selective etch process which also reduces, e.g., “thins”, a vertical thickness (vt) or vertical height extending in the third direction (D3) 611 of each of the silicon (Si) 632 layers. An etchant may be flowed into the second vertical opening 631 to selectively etch a portion of the epitaxially grow n silicon germanium (SiGe) 630 within the stack. As such, the etchant may target the first silicon germanium (SiGe) 630-1, the second silicon germanium (SiGe) 630-2, and the third silicon germanium (SiGe) 630-3 within the stack. The timed, selective etchant process may etch the silicon germanium (SiGe) 630 to entirely remove the SiGe 630 material, extending a first length (LI), from the second vertical openings 670 toform the plurality of first horizontal openings 673. As a result of the etchant process, the vertical thickness (e.g., in the third direction (D3)) of the layers of the Si material 632 occurs.

[0079] The selective etchant process may comprise a selective etch chemistry of phosphoric acid (H3PO4) or hy drogen fluoride (HF) and / or dissolving the silicon germanium (SiGe) 630 using a selective solvent, among other possible etch chemistries or solvents. Alternatively, or in addition, a selective etch to remove the silicon germanium (SiGe) 630 may consist of one or more etch chemistries selected from an aqueous etch chemistry, a semi-aqueous etch chemistry, a vapor etch chemistry, or a plasma etch chemistries, among other possible selective etch chemistries. For example, a dry etch chemistry of oxygen (02) or 02 and sulfur dioxide (SO2) may be utilized. As another example, a dry etch chemistries of 02 or of 02 and nitrogen (N2) may be used to selectively etch the silicon germanium (SiGe) 630.

[0080] The silicon germanium (SiGe) 630 has now been selectively etched isotropically to form a plurality of first horizontal openings 673 in the first region separating layers of the Si material 632.

[0081] As shown in Figure 6C, a second dielectric material 633 may be conformally deposited all around first horizontal opening 673. The second dielectric material 633 may be deposited fully around exposed surfaces in the plurality of first horizontal openings 673. The second dielectric material 633 may serve as a liner around the plurality of first horizonal openings 673. The second dielectric material 633 may be flowed into the vertical opening 631 to cover exposed surfaces of the silicon (Si) material where the silicon germanium (SiGe) was removed to form the plurality' of first horizontal openings 673 within the stack.

[0082] In one embodiment, the second dielectric material 633 may comprise a nitride material. In another embodiment, second dielectric material 633 may comprise a silicon nitride (Si3N4) material (also referred to herein as “SiN”). In another embodiment the second dielectric material 633 may include silicon dioxide (SiO2) material. In another embodiment the second dielectric material 633 may comprise a silicon oxy -carbide (SiOxCy) material, and / or combinations thereof. Embodiments are not limited to these examples.

[0083] In one embodiment, the second dielectric material 633 may be conformally deposited all around exposed surfaces in the plurality of first horizontal openings 673 to have a thickness (tl) of approximately 100 to 300 angstroms (A). Embodiments, however, are not limited to these examples.

[0084] In the example embodiment of Figure 6C, the semiconductor fabrication process can further include depositing another selectively etchable dielectric material, e.g.. the first dielectric material 639, to fill the plurality of first horizontal openings 673. For example, a first dielectric material 639, such as an oxide or other suitable spin on dielectric (SOD), is deposited into the plurality of first horizontal openings 673, on the exposed surfaces of the second dielectric material 633, to fill the first horizontal opening 673. The first dielectric material 639 may entirely fill the plurality of first horizontal openings 673. The first dielectric material 639 may be flowed into the vertical openings 631 to fill the vertical openings 631 and to fill the plurality of first horizontal openings 673 within the stack. As such, the first dielectric material 639 may fill the first horizontal openings 673 within the first silicon germanium (SiGe) 630-1, the second silicon germanium (SiGe) 630-2, and the third silicon germanium (SiGe) 630-3 within the stack.

[0085] The semiconductor fabrication process can further include selectively etching the second dielectric material 633 a second length (L2) from the second vertical openings 670 within the plurality of first horizontal openings 673. An etchant may be flowed into the second vertical opening 670 to selectively etch a portion of the second dielectric material 633 the second length (L2) from the second vertical openings 670 within the stack. As such, the etchant may target the second dielectric material 633 within the stack. The selective etchant process may etch the second dielectric material 633 the second length L2. Any selective etch chemistry described herein or otherwise may be utilized for such a selective etchant process.

[0086] Figure 6C illustrates a cross sectional view, taken along cut-line B-B’ in Figure 6A, showing another view of the semiconductor structure at this particular point in one example semiconductor fabrication process of an embodiment of the present disclosure. The cross-sectional view shown in Figure 6C is illustrated extending in the second horizontal direction (D2) 605, left and right in the plane of the drawing sheet, along an axis of the repeating iterationsof alternating layers of continuous second horizontal openings 643 and Si material 632.

[0087] In Figure 6C, first dielectric material 639 is shown spaced vertically, and extending along the first horizontal direction (DI) 609, extending into and out from the plane of the drawings sheet, for a three-dimensional array of vertically oriented memor\rcells. At the left end of the drawing sheet is shown the repeating iterations of alternating layers of the first dielectric material 639.

[0088] A first conductive material 677 may be deposited in the second vertical openings 670 to fill the first horizontal openings 673. The first conductive material 677 can be formed on a gate dielectric material 642.

[0089] As such, the semiconductor fabrication process can further include first conformally depositing the gate dielectric material 642 to form the gate dielectric material on exposed surfaces of the reduced vertical thickness (vt) of the Si material 632. For example, a gate dielectric material 642 may be formed on exposed surfaces of the Si material 632 to form horizontal access devices. In some embodiments the gate dielectric material may be an oxide material 642. In other embodiments the gate dielectric material 642 may be a high dielectric constant (K) composite material (high-K dielectric material) having a dielectric constant (K) of nine (9), or greater in value. Embodiments are not so limited. The gate dielectric material 642 may be conformally deposited fully around every surface of the Si material 632 to form gate all around (GAA) gate structures, at the channels of the access device regions.

[0090] The gate dielectric material 642 may be deposited on exposed surfaces of the Si material 632 using an atomic layer deposition. In some embodiments the gate dielectric material may be an oxide material. The oxide material, or other high-K dielectric material 642 may be selectively deposited on exposed surfaces of the Si material 632 using atomic layer deposition. A thermal oxidation process may be used to densify the ALD deposited dielectric material 642. The thermal oxidation process involves forming oxide material from a hybrid oxide material. The hybrid oxide material may combine a low temperature oxide material and a high temperature oxide material.

[0091] In the semiconductor fabrication process, a first conductive material 677 may be deposited on the gate dielectric material 642. The firstconductive material 677 may be deposited around the Si material 632 such that the first conductive material 677 may have a top portion above the Si material 632 and a bottom portion below the Si material 632 to form gate all around (GAA) gate structures, at the channels of the access device regions. The first conductive material 677 may be conformally deposited into vertical openings 670 and fill the continuous second horizontal openings 643 up to the unetched portions of the oxide material 642, the first dielectric material 639, and the second dielectric material 633. The first conductive material 677 may be conformally deposited using a chemical vapor deposition (CVD) process, plasma enhanced CVD (PECVD), atomic layer deposition (ALD), or other suitable deposition process.

[0092] In some embodiments, the first conductive material 677 may comprise one or more of a doped semiconductor (e.g., doped silicon, doped germanium, etc., a conductive metal nitride, e.g., titanium nitride, tantalum nitride, etc.), a metal (e.g., tungsten (W), titanium (Ti), tantalum (Ta), ruthenium (Ru), cobalt (Co), molybdenum (Mo), etc.), and / or a metal-semiconductor compound (e.g., tungsten silicide, cobalt silicide, titanium silicide, etc.), and / or some other combination thereof. The first conductive material 677 entwined with the gate dielectric material may form horizontally oriented access lines opposing a channel region of the epitaxially grown, single crystalline silicon (Si) material (which also may be referred to a word lines).

[0093] As shown in Figure 6C, the first conductive material 677 can be recessed to the channel regions. For example, the first conductive material 677. formed on the gate dielectric material 642, may be recessed and etched away from the third vertical opening 670. In some embodiments, the first conductive material 677 may be etched using an atomic layer etching (ALE) process. In some embodiments, the first conductive material 677 may be etched using an isotropic etch process. The first conductive material 677 may be selectively etched leaving the oxide material 642 covering the Si material 632 and the first dielectric material 639 intact. The first conductive material 677 may be selectively etched in the second direction, in the continuous second horizontal openings, a third distance (DIST 3) in a range of twenty (20) to fifty (50) nanometers (nm) back from the third vertical opening 670. The first conductivematerial 677 may be selectively etched around the Si material 632 back into the continuous second horizontal openings extending in the first horizontal direction.

[0094] The first conductive material 677 may be deposited fully around every surface of the Si material 632 on the gate dielectric material 642, to form gate all around (GAA) gate structures, at the channels of the access device regions. The first conductive material 677 may fill the spaces adjacent the bridged Si material 632. Thus, the Si material 632 may be surrounded by first conductive material 677 formed on the gate dielectric material 642.

[0095] Figure 7A illustrates an example method, at another stage of a semiconductor fabrication process, for epitaxial digit line growth in vertical three-dimensional (3D) memory, such as illustrated in Figures 1-3, and in accordance with a number of embodiments of the present disclosure. Figure 7A illustrates a top-down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments.

[0096] In the example embodiment of Figure 7 A, the second vertical openings may be filled with another selectively etchable dielectric material 767 (as shown in Figure 7C). In some embodiments the selectively etchable dielectric material may be the same dielectric material as the second dielectric material 633 shown in Figure 6C. In the example embodiment of Figure 7A another photolithographic mask may be used to form a third vertical opening 751. The third vertical opening 751 is formed using a photolithographic etchant process through the vertical stack and extending predominantly in the first horizontal direction (DI) 709. The third vertical opening 751 has been created through the stack adjacent storage node regions of the vertical 3D memory in order to form storage nodes. The method in Figures 7A-7C illustrates storage node formation, e.g., horizontally oriented capacitor cells, in the third horizontal openings.

[0097] Figure 7B illustrates a cross sectional view, taken along cut-line A-A’ in Figure 7A, showing another view of the semiconductor structure at this particular point in one example semiconductor fabrication process of an embodiment of the present disclosure. As will be shown and described more in connection with Figure 7C. the completed horizontally oriented capacitor cells are shown in this cross sectional view having first electrodes 761, e.g., bottomcell contact electrodes, cell dielectrics 763, and second electrodes 756, e.g., top, common node electrodes, on a semiconductor substrate 700 to form the vertical stack.

[0098] As shown in Figure 7B, a vertical direction 711 is illustrated as a third direction (D3), e.g., z-direction in an x-y-z coordinate system, analogous to the third direction (D3) 711, among first, second, and third directions, shown in Figures 1-3. The plane of the drawing sheet, extending right and left, is in a first direction (DI) 709.

[0099] In the example embodiment of Figure 7B, the first electrodes 761, e.g.. bottom electrodes to be connected to source / drain regions of horizontal access devices, and second electrodes 756 are illustrated separated by a cell dielectric material 763 extending into and out of the plane of the drawing sheet in second direction (D2) and along an axis of orientation of the horizontal access devices and horizontal storage nodes of the arrays of vertically stacked memory cells of the three dimensional (3D) memory.

[0100] Figure 7C illustrates a cross sectional view, taken along cut-line B-B’ in Figure 7A, showing another view of the semiconductor structure at this particular point in one example semiconductor fabrication process of an embodiment of the present disclosure. The cross-sectional view shown in Figure 7C is illustrated extending in the second horizontal direction (D2) 705, left and right along the plane of the drawing sheet, along an axis of the sacrificial oxide material 738 and Si material 732 along and in which the horizontally oriented access devices and horizontally oriented storage nodes, e.g., capacitor cells, can be formed within the layers of Si material 732.

[0101] In the example embodiment of Figure 7C, the horizontally oriented storage nodes, e.g., capacitor cells, are illustrated as having been formed in this semiconductor fabrication process and first electrodes 761, e.g., bottom electrodes to be connected to source / drain regions of horizontal access devices, and second electrodes 756. e.g., top electrodes to be connected to a common electrode plane such as a ground plane, separated by cell dielectrics 763, are shown. How ever, embodiments are not limited to this example. In other embodiments, the first electrodes 761, e.g.. bottom electrodes to be connected to source / drain regions of horizontal access devices, and second electrodes 756, e.g., top electrodes to be connected to a common electrode plane such as aground plane, separated by cell dielectrics 763, may be formed subsequent to forming a first source / drain region, a channel region, and a second source / drain region in a region of the Si material 732, intended for location, e.g., placement formation, of the horizontally oriented access devices.

[0102] In the example embodiment of Figure 7C, the horizontally oriented storage nodes having the first electrodes 761, e.g., bottom electrodes, connected to second source / drain regions of horizontal access devices. In some embodiments the second source / drain regions may be doped using gas phase doping or other suitable doping techniques before the first electrodes 761 are formed. Second electrodes 756, e.g., top electrodes, connected to a common electrode plane such as a ground plane, are shown formed in a second horizontal opening 751 and separated from the first electrodes 761 by the cell dielectrics 763. The second electrodes 756 may extend in second direction (D2) 705, left and right in the plane of the drawing sheet, a third distance from the third vertical opening, e.g.. 751 in Figure 7B, formed in the vertical stack, and may extend in to an interior of the first electrodes 761. In some embodiments, as shown in Figure 7C, the second electrodes 756 may oppose an interior and exterior surfaces of the first electrodes 761 to form double sided storage nodes, e.g.. capacitors, as separated by the cell dielectric along an axis of orientation of the horizontal access devices and horizontal storage nodes of the arrays of vertically stacked memory cells of the three dimensional (3D) memory.

[0103] Figure 8A illustrates an example method, at another stage of a semiconductor fabrication process, for forming epitaxial silicon within horizontal access devices in vertical three-dimensional (3D) memory, such as illustrated in Figures 1-3, and in accordance with a number of embodiments of the present disclosure. Figure 8A illustrates a top down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments.

[0104] The method in Figure 8A further illustrates using a photolithographic mask to reopen the second vertical opening 855 adjacent the access device regions. In Figures 8A-8C, one or more selective etchant processes may be used to reopen the second vertical opening 851 in the access device region through the vertical stack and extending predominantly in the first horizontal direction (DI) 809. The one or more selective etchant processesreforms the second vertical opening, e.g., a fourth vertical opening 851, to reexpose sidewalls in the repeating iterations of alternating layers of silicon (Si), first dielectric material 839, and dielectric material 867 in the first horizontal openings 863. The dielectric material 867, e.g., same dielectric material as second dielectric material 833, may remain to separate and isolated the recessed first conductive material 877.

[0105] Figure 8B illustrates a cross sectional view, taken along cut-line A-A’ in Figure 8A, showing another view of the semiconductor structure at this particular point in one example semiconductor fabrication process of an embodiment of the present disclosure. The cross-sectional view shown in Figure 8B is away from the plurality of separate, horizontal access lines 877, and shows repeating iterations of alternating layers of second electrodes 856 separated by horizontally oriented capacitor cells having first electrodes 861, e.g., bottom cell contact electrodes, cell dielectrics 863, and top, common node electrodes, on a semiconductor substrate 800 to form the vertical stack remain. As shown in Figure 8B, a vertical direction 81 1 is illustrated as a third direction (D3), e.g., z- direction in an x-y-z coordinate system, analogous to the third direction (D3) 811, among first, second, and third directions, shown in Figures 1-3. The plane of the drawing sheet, extending right and left, is in a first direction (DI) 809.

[0106] In the example embodiment of Figure 8B, the first electrodes 861, e g., bottom electrodes to be connected to source / drain regions of horizontal access devices, and second electrodes 856 are illustrated separated by a cell dielectric material 863 extending into and out of the plane of the drawing sheet in second direction (D2) and along an axis of orientation of the horizontal access devices and horizontal storage nodes of the arrays of vertically stacked memory cells of the three dimensional (3D) memory.

[0107] Figure 8C illustrates a cross sectional view, taken along cut-line B-B’ in Figure 8A, showing another view of the semiconductor structure at this particular point in one example semiconductor fabrication process of an embodiment of the present disclosure. The cross sectional view shown in Figure 8C is illustrated extending in the second horizontal direction (D2) 805, left and right along the plane of the drawing sheet, along an axis of the repeating iterations of alternating layers of second electrodes 856 along and in which the horizontally oriented access devices and horizontally oriented storage nodes.e.g., capacitor cells, can be formed within the layers of epitaxially grown, single crystalline silicon (Si) material 832.

[0108] In the example embodiment of Figure 8C, the horizontally oriented storage nodes, e.g., capacitor cells, are illustrated as having been formed in this semiconductor fabrication process and first electrodes 861, e.g., bottom electrodes to be connected to source / drain regions of horizontal access devices, and second electrodes 856. e.g., top electrodes to be connected to a common electrode plane such as a ground plane, separated by cell dielectrics 863, are shown. In this embodiment, a dual-sided capacitor is illustrated as an alternative to the single-sided capacitor. However, embodiments are not limited to this example. In other embodiments, the first electrodes 861, e.g., bottom electrodes to be connected to source / drain regions of horizontal access devices, and second electrodes 856, e.g., top electrodes to be connected to a common electrode plane such as a ground plane, separated by cell dielectrics 863, may be formed subsequent to forming a first source / drain region, a channel region, and a second source / drain region in a region of the epitaxially grown, single crystalline silicon (Si) material 832, intended for location, e.g., placement formation, of the horizontally oriented access devices.

[0109] In the example embodiment of Figure 8C, the horizontally oriented storage nodes having the first electrodes 861, e.g., bottom electrodes to be connected to source / drain regions of horizontal access devices, and second electrodes 856, e.g., top electrodes to be connected to a common electrode plane such as a ground plane, are shown formed in a third horizontal opening, extending in second direction (D2) 805, left and right in the plane of the drawing sheet, a third distance from the vertical opening formed in the vertical stack, and along an axis of orientation of the horizontal access devices and horizontal storage nodes of the arrays of vertically stacked memory cells of the three dimensional (3D) memory.

[0110] In Figure 8C, a neighboring, horizontal access line 877 is illustrated adjacent the second dielectric material 833, with a portion of the first conductive material 877 located above the Si material 832, and a portion of the first conductive material 877 located below- the Si material 832 indicating a location set inward from the plane and orientation of the drawing sheet.

[0111] The first and the second source / drain regions may be formed by gas phase doping a dopant in a side surface of the Si material 832 from the third horizontal openings to form second source / drain regions horizontally adjacent the channel region; and depositing horizontally oriented capacitor cells having a bottom electrode formed in electrical contact with the second source / drain regions. In some embodiments, the dielectric material 867 has been removed from the fourth vertical openings 855, but remains filling the first horizontal openings 863 separating the continuous first conductive material 877, running into and out from the plane of the drawing sheet, up to the unetched portions of the oxide material 839 and fourth vertical opening 855.

[0112] Figure 9A illustrates an example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line grow th in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure. Figure 9A illustrates a top- down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The top-down view in Figure 9A is illustrated extending in a first horizontal direction (DI) 909 and a second horizontal direction (D2) 905 within the fourth vertical opening 855 in Figure 8C.

[0113] Figure 9A illustrates a top-down view of the stack following the deposition of the first dielectric material 939 and following recess of the SiGe material, previously described in connection with Figures 6A-6C. A risk of horizontally merging epitaxial grown Si material can be present when epitaxially growing the Si material vertically to form a vertically oriented digit line. In this example, the Si material can be sculpted to promote vertical merging of epitaxially grown Si material before horizontal merging, as is further described herein.

[0114] Figure 9B illustrates an example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure. Figure 9B illustrates a top- down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The top-down view in Figure 9B is illustrated extending in a first horizontal direction(DI) 909 and a second horizontal direction (D2) 905 within the fourth vertical opening 855 in Figure 8C.

[0115] As illustrated in Figure 9B, the dielectric material 939 can be selectively etched to recess the dielectric material 939 back from the fourth vertical opening 855 in Figure 8C. For example, the semiconductor fabrication process can include recessing the dielectric material 939 adjacent to the Si material 932 to expose edge surfaces 980-1, 980-2, 980-3 along the first and the second directions (D1 / D2 909 / 905) of the Si material 932. The dielectric material 939 can be recessed by a suitable timed selective etch process to a chosen distance from the fourth vertical opening 855 in Figure 8C. Various etch processes may be utilized to recess the dielectric material 939 to expose the edge surfaces 980-1, 980-2, 980-3 of the Si material 932.

[0116] Figure 9C illustrates an example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory’ in accordance with a number of embodiments of the present disclosure. Figure 9C illustrates a top- down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The top-down view in Figure 9C is illustrated extending in a first horizontal direction (DI) 909 and a second horizontal direction (D2) 905 within the fourth vertical opening 855 in Figure 8C.

[0117] Following recessing the dielectric material 939, the edge surfaces 980-1, 980-2, 980-3 of the Si material 932 can be exposed. Accordingly, the semiconductor fabrication process can include a timed selective etch to remove Si material 932 from the exposed edge surfaces 980-1, 980-2, 980-3 of the Si material 932 perpendicular to an axis extending in the first horizontal direction DI 909, perpendicular to an axis extending in the second horizontal direction D2 905, as well as perpendicular to an axis extending in the third direction D3 (not shown in Figures 9A-9C). Sculpting the Si material 932 to remove Si material 932 can reduce a width dimension of the Si material 932 (e g., along an axis extending in the DI direction 909), a length dimension of the Si material 932 (e g., along an axis extending in the D2 direction 905) and a height dimension of the Si material 932 (e.g., along an axis extending in the third, D3 direction (not shown)).

[0118] Removing the Si material 932 can be performed by thinning the exposed edges 980-1. 980-2, 980-3 of the Si material 932 using a wet etch process. The wet etch process can include an ammonia-peroxide mixture (APM) wet etch process to thin the exposed edges 980-1, 980-2, 980-3 of the Si material 932. However, embodiments of the disclosure are not limited to an APM wet etch process. For example, any other etch chemistry can be utilized.

[0119] As mentioned above, thinning the exposed edges 980-1, 980-2, 980-3 of the Si material 932 can promote vertical merging of epitaxially grow n Si material before horizontal merging. Thinning the exposed edges 980-1, 980- 2, 980-3 of the Si material 932 as described in Figures 9A-9C can provide for a simple way to sculpt the exposed edges 980-1. 980-2, 980-3 of the Si material 932. Following the thinning, the semiconductor fabrication process can further include epitaxially growing Si material from the thinned exposed edge surfaces 980-1, 980-2, 980-3 of the Si material 932 to form continuous, vertically oriented digit lines (e.g., as is further illustrated and described in connection with Figures 13A-13B). Due to the reduced width dimension in the DI direction 909, epitaxial growth of Si material from the thinned exposed edges 980-1, 980-2, 980-3 of the Si material 932 can result in vertical merging of epitaxially grown Si material before horizontal merging. Such an approach can prevent horizontal short-circuiting of adjacent vertically oriented digit lines in the 3D memory array.

[0120] Figure 10A illustrates another example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure. Figure 10A illustrates a cross-sectional view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The cross-sectional view in Figure 10A is illustrated extending in a second horizontal direction (D2) 905, left to right in the plane of the drawing sheet from the fourth vertical opening 855 in Figure 8C on a left-hand side of the drawing sheet, and having the first conductive material 1077 above and below the silicon (Si) material 1032 opposing a channel region in the vertical direction (D3) 1011.

[0121] Figure 10A illustrates a cross-sectional view of the stack following formation of horizontal access lines, previously described inconnection with Figures 6A-6C. As previously mentioned, in some examples, a risk of horizontal merging of Si material can be present when epitaxially- growing the Si material to form a vertically oriented digit line. In this example, the Si material can be sculpted to promote vertical merging, in the third direction (D3) 1011, of epitaxially grown Si material, before horizontal merging, e.g., in the first direction (DI) (not shown), to form separate, epitaxially grown vertical digit lines, as is further described herein.

[0122] Figure 10B illustrates another example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure. Figure 10B illustrates a cross-sectional view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The cross-sectional view in Figure 10B is illustrated extending in a second horizontal direction (D2) 1005 and a vertical direction (D3) 1011.

[0123] As illustrated in Figure 10B, the dielectric material 1067 filled in the fourth vertical opening 1055 has been selectively etched to recess from the fourth vertical opening 1055. For example, the semiconductor fabrication process can include recessing the dielectric material 1067 adjacent to the Si material 1032 to expose edge surfaces 1080-2. 1080-4, 1080-5, 1080-6 of the Si material 1032. The dielectric material 1067 can be recessed by a timed selective etch to expose edge surfaces 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032. However, embodiments are not so limited.

[0124] Figure 10C illustrates another example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory in accordance with a number of embodiments of the present disclosure. Figure 10C illustrates a cross-sectional view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The cross-sectional view in Figure 10C is illustrated extending in a second horizontal direction (D2) 905 and a vertical direction (D3) 1011.

[0125] Following recessing the dielectric material 1067, the edge surfaces 1080-2, 1080-4, 1080-5. 1080-6 of the Si material 1032 can be exposed. Accordingly, the semiconductor fabrication process can include removing Simaterial 1032 from the exposed edge surfaces 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032 perpendicular to an axis extending in the first horizontal direction DI (not shown) and perpendicular to an axis extending in the third direction D3 1011. Sculpting the Si material 1032 to remove Si material 1032 can reduce a width dimension of the Si material 1032 (e.g., along an axis extending in the DI direction) and a height dimension of the Si material 1032 (e.g., along an axis extending in the third D3 direction 1011).

[0126] Removing the Si material 1032 can be performed by thinning the exposed edges 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032 using a wet etch process. The wet etch process can include an APM wet etch process to thin the exposed edges 1080-2. 1080-4, 1080-5, 1080-6 of the Si material 1032. However, embodiments of the disclosure are not limited to an APM wet etch process. For example, any other etch chemistry can be utilized.

[0127] As mentioned above, thinning the exposed edges 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032 can promote vertical merging of epitaxially grown Si material before horizontal merging. Thinning the exposed edges 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032 as described in Figures 10A-10C can provide for a simple way to sculpt the exposed edges 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032 without curvature issues on the Si material 1032 which may cause issues during fill and recessing during access device formation. Following the thinning, the semiconductor fabrication process can further include epitaxially growing Si material from the thinned exposed edge surfaces 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032 to form continuous, vertically oriented digit lines (e.g., as is further illustrated and described in connection with Figures 13A-13B). Due to the reduced width dimension in the DI direction (extending into and out of the page as oriented in Figure 10C), epitaxial growth of Si material from the thinned exposed edges 1080-2, 1080-4, 1080-5, 1080-6 of the Si material 1032 can result in vertical merging of epitaxially grown Si material before horizontal merging. Such an approach can prevent horizontal short-circuiting of adjacent vertically oriented digit lines in the 3D memory array.

[0128] Figure 11 A illustrates another example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory in accordance witha number of embodiments of the present disclosure. Figure 11 A illustrates a top- down view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The top-down view in Figure 11 A is illustrated extending in a first horizontal direction (DI) 1109 and a second horizontal direction (D2) 1105.

[0129] Figure 11 A illustrates a top-down view of the stack following formation of horizontal access lines, previously described in connection with Figures 6A-6C. As previously mentioned, in some examples, a risk of horizontal merging of Si material can be present when epitaxially growing the Si material to form a vertically oriented digit line. In this example, the Si material can be sculpted to promote vertical merging of epitaxially grown Si material before horizontal merging, as is further described herein.

[0130] As previously described in connection with Figures 5A-5C, a plurality of second vertical openings can be formed through the vertical stack having a first horizontal direction DI 1109 and a second horizontal direction D2 1105 that can define elongated vertical columns (e.g., 513-1, 513-2, 513-M previously illustrated in Figure 5A) with vertical sidewalls in the stack separating memory cells on each level. A doped dielectric material 1139 can be filled in the second vertical openings, using a process such as CVD. The doped dielectric material 1139 can be, for instance, phosphorus doped, arsenic doped, or boron doped dielectric material.

[0131] The semiconductor fabrication process can include laterally doping adjacent portions of the Si material 1132 in the first horizontal direction 1109 (e.g., direction DI). For example, the Si material 1132 can be doped using a phosphorous diffusion technique to form the doped Si material 1 182, to a given depth, separating the Si material 1132 from the dielectric material 1139. In some embodiments a timed, thermal doping diffusion technique may be used to form the doped Si material 1139 to a given depth in the Si material 1132. In some embodiments the lateral doping can achieve doping in edge surfaces of the Si material, e.g., in a plane perpendicular to the first horizontal direction DI 1109.

[0132] Figure 1 IB illustrates another example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth that connects vertically before laterally in vertical three-dimensional (3D) memory' in accordance with a number of embodiments of the present disclosure. Figure 1 IB illustrates a cross-sectional view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The cross-sectional view in Figure 1 IB is illustrated extending in a first horizontal direction (DI) 1109 and a vertical direction (D3) 1011, taken for example along cut-line D-D’ in Figure 8 A.

[0133] As illustrated in Figure 11B, portions of the Si material 1132 have been doped, resulting in doped Si material 1182 at the edges of the Si material 1132. At this point in the semiconductor manufacturing process, the doped Si material 1182 and Si material 1132 can be oriented in alternating layers in a stack between dielectric material 1167. The doped Si material 1182 at the edges of the Si material 1132 can form etch selectivity difference as compared with the undoped, epitaxially grown Si material 1132.

[0134] Figure 11C illustrates another example method, at another stage of a semiconductor fabrication process, for sculpting Si material for epitaxial digit line growth in vertical three-dimensional (3D) memory7in accordance with a number of embodiments of the present disclosure. Figure 11C illustrates a cross-sectional view of a semiconductor structure, at a particular point in time, in a semiconductor fabrication process, according to one or more embodiments. The cross-sectional view in Figure 1 1C is illustrated extending in a first horizontal direction (DI) 1109 and a vertical direction (D3) 1111 in the plane of the draw ing sheet.

[0135] Following doping of the edge surfaces of the Si material 1132 (e.g., resulting in the doped, epitaxial Si material 1 182), the semiconductor fabrication process can include removing the doped Si material 1182 from the undoped, epitaxial Si material 1132. Sculpting the Si material 1132 to remove the doped Si material 1182 can reduce a width dimension of the Si material 1132 (e.g., along an axis extending in the DI direction) without affecting, e.g., reducing, or “thinning” a vertical thickness (vt), the Si material 1132 in the vertical direction 1111 (e.g., direction D3 1111).

[0136] Removing the doped Si material 1182 can be performed by selectively etching the doped Si portions 1182 adjacent the undoped, epitaxial Si material 1132 (e.g., the doped Si material 1182). In a timed selective etchprocess the doped Si material 1182 can be removed a first distance in the first horizontal direction DI 1109 from the doped dielectric material 1139. e.g., first dielectric material, in the second vertical openings to expose thinned edge surfaces 1183 and resulting in a reduced width (Wl) in the first horizonal direction DI 1109 of epitaxial Si material 1132. According to embodiments, an etchant may be flowed into the first vertical opening to perform a timed selective etch of the doped Si material 1182 to a particular depth in the second horizontal direction D2 1105, into the plane of the drawing sheet in Figure 11C. The selective etchant process may include a suitable selective etch chemistry' to selectively remove the doped epitaxial Si material 1182.

[0137] As mentioned above, exposing the thinned edge surfaces 1183 of the Si material 1032 can promote vertical merging of epitaxially grow n Si material before horizontal merging. Exposing the thinned edge surfaces 1183 as described in Figures 11 A-l 1C can provide for a more controlled way to sculpt the Si material 1132, promoting removal of Si material 1132 in the horizontal direction DI (e.g., 1109) without removal of Si material 1132 in the vertical direction D3 (e.g., 1111).

[0138] Follow ing exposing the thinned edges 1183 of the Si material 1132 and selective etch recess of the dielectric material 1167 in the second horizontal direction D2 1105, into the plane of the drawing sheet in Figure 11C. the semiconductor fabrication process can further include epitaxially growing Si material from the exposed thinned edges 1183 of the Si material 1132 to form continuous, vertically oriented digit lines (e.g., as is further illustrated and described in connection with Figures 13A-13B). Due to the reduced width dimension (Wl) in the DI direction (extending left and right along the plane of the drawing sheet in Figure 11C), epitaxial growth of Si material from the exposed thinned edges 1183 of the Si material 1132 can result in vertical merging of epitaxially grown Si material before horizontal merging. Such an approach can prevent horizontal short-circuiting of adjacent vertically onented digit lines in the 3D memory array. As a result, separated, vertical digit lines may be formed as described further in connection with Figures 13A-13B.

[0139] Figure 12A is a cross-sectional view' showing another view' of the semiconductor structure at a particular time in the semiconductor fabrication process. In Figure 12A, as in earlier embodiments, a first source / drain region ofthe epitaxial Si material to form horizontal access devices has been exposed and first timed amount of epitaxial growth can be initiated from the first vertical opening. Figure 12A illustrates this epitaxial silicon (Si) growth 1284. Figure 12 A further illustrates that the epitaxial Si growth rate may occur substantially uniformly from each crystalline plane surface, e.g., cry stalline planes <100>, <110>, and <111>, result in the substantially uniform epitaxial Si growth 1284 illustrated in Figure 12A in the first, e.g.. horizontal, direction DI 1209 (left to right directions in the plane of the drawing sheet) as well as the third, e.g., vertical, direction D3 1211 (top to bottom directions in the plane of the drawing sheet). The cross-sectional view in Figure 12A is illustrated extending in a first horizontal direction (DI) 1209 and a vertical direction (D3) 1211.

[0140] In the example embodiment shown in Figures 12A-12D, the Silicon material 1232 may be sculpted by oxidation. In this embodiment, and as explained further below; epitaxially grown Si material 1132 is treated and removed under controlled conditions to encourage epitaxial growth merger in a vertical direction first, since oxidation of the epitaxially grown Si 1284 can occur more rapidly along particular cry stalline plane surfaces of the epitaxially grown Si 1284 than others, e.g., faster in a direction perpendicular to the <110> and <111> crystalline plane surfaces than perpendicular to the <100> crystalline plane surfaces.

[0141] For example, the timed controlled epitaxial Si growth 1284 as showm in Figure 12A may be halted, and a timed oxidation process of the exposed surfaces of the epitaxial Si growth 1284 may be initiated in Figures 12B. As shown in Figure 12A the semiconductor fabrication process can include epitaxially growing a first amount of Si material 1284 from the Si material 1232 from the first source / drain regions. During growth of the first amount of Si material 1284, epitaxial growth of the first amount of Si material 1284 can occur vertically along a <100> atomic crystalline plane orientation corresponding to the third direction D3 1211. Additionally, epitaxial growth of the first amount of Si material 1284 can occur horizontally in a first direction D 1 1209 along a <110> atomic cry stalline plane orientation, and horizontally in a second horizontal direction (e.g., extending outwards from the page) along a <110> atomic crystalline plane orientation.

[0142] All of this epitaxial grow th along different planes may occur at substantially a uniform rate from exposed surfaces oriented in different crystalline planes. Thus, during the growth of the first amount of Si material 1284, as illustrated in Figure 12A, growth of the first amount of Si material 1284 in the first horizontal direction 1209 (e.g., DI) results in the first amount of Si material 1284 being close to merging in the first horizontal direction 1209. To prevent this horizontal merging, a portion of the first amount of Si material 1284 can be treated and removed, as is further described herein.

[0143] Figure 12B is a cross-sectional view showing another view of the semiconductor structure at a particular time in the semiconductor fabrication process. In Figure 12B, a portion of the first amount of Si material 1284 can be oxidized. The cross-sectional view in Figure 12B is illustrated extending in a first horizontal direction (DI) 1209 and a vertical direction (D3) 1211.

[0144] As shown in Figure 12B, the semiconductor fabrication process can include oxidizing exposed surfaces of the first amount of epitaxially grown Si material 1284 to form oxidized epitaxial Si material 1286. The oxidation process can be performed using thermal oxidation. In some examples, the exposed surfaces of the first amount of Si material 1284 can be oxidized using a dry oxidation process. In some examples, the exposed surfaces of the first amount of Si material 1284 can be oxidized using a wet oxidation process.

[0145] As shown in Figure 12B, oxidizing the exposed surfaces of the first amount of Si material 1284 can result in the first amount of Si material 1284 being oxidized more in the first horizontal direction DI (e.g., 1209) than in the vertical direction D3 (e.g., 1211), e.g., in a direction perpendicular to the <110> crystalline plane (horizontally) than in a direction perpendicular <100> crystalline plane (vertically). For example, oxidizing exposed surfaces of the first amount of Si material 1284 occurs at a slower rate on the <100> crystalline plane surface in the third direction than an oxidization rate on the <110> crystalline plane surface and the <111> crystalline plane surface, e.g.. more slowly in the third direction D3 1211 (vertically), than in the first direction DI 1209 (horizontally, left to right in the plane of the drawing sheet) and the second direction D2 1205 (horizontally, extending out of the plane of the drawing sheet).

[0146] Figure 12C is a cross-sectional view showing another view of the semiconductor structure at a particular time in the semiconductor fabrication process. In Figure 12C, oxidized epitaxial Si material 1286 can be removed. The cross-sectional view in Figure 12C is illustrated extending in a first horizontal direction (DI) 1209 and a vertical direction (D3) 1211.

[0147] The semiconductor fabrication process can include removing the oxidized epitaxial Si material. Removing the oxidized epitaxial Si material can include etching the oxidized epitaxial Si material using a wet etch process. The wet etch process can be performed utilizing any suitable wet etch chemistry.

[0148] Removing the oxidized epitaxial Si material can expose a remaining portion of epitaxial Si material 1288. As illustrated in Figure 12C. removing the oxidized epitaxial Si material can open space in the first horizontal direction 1209 (e.g., DI) more than in the vertical direction 1211 (e.g., D3). Opening the space in the first horizontal direction 1209 can allow for further epitaxial growth of the Si material where vertical merging of the epitaxially grown Si material occurs before horizontal merging, as is further described herein.

[0149] Figure 12D is a cross-sectional view showing another view' of the semiconductor structure at a particular time in the semiconductor fabrication process. In Figure 12D, Si material can be epitaxially grown a second amount from the remaining portion of epitaxial Si material. The cross-sectional view in Figure 12D is illustrated extending in a first horizontal direction (DI) 1209 and a vertical direction (D3) 1211.

[0150] The semiconductor fabrication process can include epitaxially growing a second amount of Si material 1290 from the remaining portion of the epitaxially grown Si material until the epitaxially grown Si material vertically merges. Due to the opened space in the first horizontal direction 1209 (e.g., DI) resulting from removing oxidized epitaxial Si material, the second amount of epitaxially grown Si material 1290 can be grown from the remaining portion of epitaxial Si material such that the second amount of epitaxially grown Si material 1290 merges to form continuous, vertically oriented digit lines 1292 in the first vertical openings.

[0151] Although one instance of oxidation of Si material and removal of oxidized Si material is described above, embodiments of the present disclosureare not so limited. For example, Si material may be oxidized and removed and further epitaxial growth of Si material can occur multiple times to trim horizontal epitaxial Si material growth. Such a process as described above may be repeated until a desired contact size is achieved.

[0152] Figure 13A is a cross-sectional view, taken along cut-line A-A’ in Figure 8A, showing another view of the semiconductor structure at a particular time in the semiconductor fabrication process. In Figure 13 A. the epitaxially grown Si material 1290 can be grown to a point at which it merges in the vertical direction (e.g., direction 1311, D3) to form a continuous, vertically oriented digit line 1392.

[0153] Figure 13B is a cross-sectional view, taken along cut-line B-B’ in Figure 8A, showing another view of the semiconductor structure at a particular time in the semiconductor fabrication process. As illustrated in Figure 13B, the epitaxially grown Si material 1392 from each of the first source / drain regions (e g., from the exposed Si material 1332) at each level of the stack has merged to form continuous, vertically oriented digit lines 1392 comprised of epitaxially grown Si material 1390.

[0154] At this point in the semiconductor fabrication process, the continuous, vertically oriented digit lines 1392 are still Si material. For example, the vertically oriented digit lines 1392 are still epitaxially grown Si material. As such, the semiconductor fabrication process can further include converting the continuous, vertically oriented digit lines 1392 from the Si material to a conductive material having a different characteristic from the Si material.

[0155] The epitaxially grown Si material of the vertically oriented digit lines 1392 can be converted to conductive material (e.g., tungsten material). For instance, a tungsten hexafluoride (WF6) material can be selectively reacted with the remaining Si material. For example, the tungsten hexafluoride material can be flowed into the third vertical opening 1370 to expose the digit line 1392 to the tungsten hexafluoride material, such that the (e.g., exposed) vertically oriented digit lines 1392 are soaked with the tungsten hexafluoride, causing the tungsten material to grow. This reaction can be expressed chemically as:with the change in enthalpy for the reaction being -1908 KJ / mole. The tungsten hexafluoride may target all iterations of the vertically oriented digit lines 1392 in the stack.

[0156] The tungsten hexafluoride material, however, may react only with the epitaxially grown Si material. For instance, the tungsten hexafluoride material may not react with dielectric material, source / drain region, or oxide material. Hence, the conversion process may be selective to the epitaxially grown Si material of the continuous, vertically oriented digit lines 1392. For instance, the dielectric material, source / drain region, and oxide material may be left intact during the conversion process, and the source / drain region may remain nearly untouched by the conversion process.

[0157] As such, the epitaxially grown Si material can be converted into a conductive material to function as a vertically oriented digit line. The vertically oriented digit line formation as described above can be utilized in vertical openings having high aspect ratios, such as 5: 1 vertical / horizontal aspect ratio specifications, or even higher.

[0158] Figure 14 is a block diagram of an apparatus in the form of a computing system 1400 including a memory' device 1403 in accordance with a number of embodiments of the present disclosure. As used herein, a memory device 1403, a memory array 1410, and / or a host 1402, for example, might also be separately considered an “apparatus.” According to embodiments, the memory' device 1403 may comprise at least one memory' array 1410 with a memory cell formed having a digit line and body contact, according to the embodiments described herein.

[0159] In this example, system 1400 includes a host 1402 connected to memory' device 1403 via an interface 1404. The computing system 1400 can be a personal laptop computer, a desktop computer, a digital camera, a mobile telephone, a memory card reader, or an Intemet-of-Things (loT) enabled device, among various other types of systems. Host 1402 can include a number of processing resources (e g., one or more processors, microprocessors, or some other type of controlling circuitry ) capable of accessing memory' 1403. The system 1400 can include separate integrated circuits, or both the host 1402 and the memory device 1403 can be on the same integrated circuit. For example, the host 1402 may be a system controller of a memory7system comprising multiplememory devices 1403, with the system controller 1402 providing access to the respective memory devices 1403 by another processing resource such as a central processing unit (CPU).

[0160] In the example shown in Figure 14, the host 1402 is responsible for executing an operating system (OS) and / or various applications (e g., processes) that can be loaded thereto (e.g., from memory’ device 1403 via controller 1402). The OS and / or various applications can be loaded from the memory’ device 1403 by providing access commands from the host 1402 to the memory’ device 1403 to access the data comprising the OS and / or the various applications. The host 1402 can also access data utilized by the OS and / or various applications by providing access commands to the memory device 1403 to retrieve said data utilized in the execution of the OS and / or the various applications.

[0161] For clarity, the system 1400 has been simplified to focus on features with particular relevance to the present disclosure. The memory array 1410 can be a DRAM array comprising at least one memory cell having a digit line and body' contact formed according to the techniques described herein. For example, the memory’ array 1410 can be an unshielded DL 4F2 array such as a 3D-DRAM memory array. The array 1410 can comprise memory cells arranged in rows connected by word lines (which may be referred to herein as access lines or select lines) and columns connected by digit lines (which may be referred to herein as sense lines or data lines). Although a single array 1410 is shown in Figure 14, embodiments are not so limited. For instance, memory device 1403 may include a number of arrays 1410 (e.g.. a number of banks of DRAM cells).

[0162] The memory' device 1403 includes address circuitry 1406 to latch address signals provided over an interface 1404. The interface can include, for example, a physical interface employing a suitable protocol (e.g., a data bus, an address bus, and a command bus, or a combined data / address / command bus). Such protocol may be custom or proprietary, or the interface 1404 may employ a standardized protocol, such as Peripheral Component Interconnect Express (PCIe), Gen-Z, CCIX, or the like. Address signals are received and decoded by a row decoder 1408 and a column decoder 1412 to access the memory array 1410. Data can be read from memory array 1410 by sensing voltage and / or current changes on the sense lines using sensing circuitry 1411. The sensingcircuitry 1411 can comprise, for example, sense amplifiers that can read and latch a page (e.g.. row) of data from the memory array 1410. The I / O circuitry- 1407 can be used for bi-directional data communication with the host 1402 over the interface 1404. The read / write circuitry 1413 is used to write data to the memory array 1410 or read data from the memory array 1410. As an example, the circuitry 1413 can comprise various drivers, latch circuitry, etc.

[0163] Control circuitry 1405 decodes signals provided by the host 1402. The signals can be commands provided by the host 1402. These signals can include chip enable signals, wri te enable signals, and address latch signals that are used to control operations performed on the memory array 1410, including data read operations, data write operations, and data erase operations. In various embodiments, the control circuitry 1405 is responsible for executing instructions from the host 1402. The control circuitry 1405 can comprise a state machine, a sequencer, and / or some other t pe of control circuitry-, which may be implemented in the form of hardware, firmware, or software, or any combination of the three. In some examples, the host 1402 can be a controller external to the memory- device 1403. For example, the host 1402 can be a memory- controller which is connected to a processing resource of a computing device.

[0164] The term semiconductor can refer to, for example, a material, a wafer, or a substrate, and includes any base semiconductor structure. “Semiconductor” is to be understood as including silicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI) technology7, thin-film-transistor (TFT) technology, doped and undoped semiconductors, epitaxial silicon supported by a base semiconductor structure, as well as other semiconductor structures.Furthermore, when reference is made to a semiconductor in the preceding description, previous process steps may have been utilized to form regions / j unctions in the base semiconductor structure, and the term semiconductor can include the underlying materials containing such regions / junctions.

[0165] The figures herein follow a numbering convention in which the first digit or digits correspond to the drawing figure number and the remaining digits identify an element or component in the drawing. Similar (e.g., the same) elements or components between different figures may- be identified by the use of similar digits. As will be appreciated, elements shown in the variousembodiments herein can be added, exchanged, and / or eliminated so as to provide a number of additional embodiments of the present disclosure. In addition, as will be appreciated, the proportion and the relative scale of the elements provided in the figures are intended to illustrate the embodiments of the present disclosure and should not be taken in a limiting sense.

[0166] As used herein, “a number of’ or a “quantity of' something can refer to one or more of such things. For example, a number of or a quantity of memon cells can refer to one or more memory cells. A “plurality” of something intends two or more. As used herein, multiple acts being performed concurrently refers to acts overlapping, at least in part, over a particular time period. As used herein, the term “connected” may include electrically connected, directly connected, and / or directly connected with no intervening elements (e.g., by direct physical contact), indirectly connected and / or connected with intervening elements, or wirelessly connected. The term connected may further include two or more elements that co-operate or interact with each other (e.g., as in a cause and effect relationship). An element connected between two elements can be between the two elements and connected to each of the two elements.

[0167] It should be recognized the term vertical accounts for variations from “exactly” vertical due to routine manufacturing, measuring, and / or assembly variations and that one of ordinary skill in the art would know what is meant by the term “perpendicular.” For example, the vertical can correspond to the z-direction. As used herein, when a particular element is “adjacent to” an other element, the particular element can cover the other element, can be over the other element or lateral to the other element and / or can be in direct physical contact the other element. Lateral to may refer to the horizontal direction (e.g., the y-direction or the x-direction) that may be perpendicular to the z-direction, for example.

[0168] Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will appreciate that an arrangement calculated to achieve the same results can be substituted for the specific embodiments shown. This disclosure is intended to cover adaptations or variations of various embodiments of the present disclosure. It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combination of the above embodiments, and otherembodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments of the present disclosure includes other applications in which the above structures and methods are used. Therefore, the scope of various embodiments of the present disclosure should be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled.

Claims

What is claimed is:

1. A method for forming arrays of vertically stacked memory cells, having horizontally oriented access devices and storage nodes, comprising: forming a vertical stack having alternating layers of silicon germanium (SiGe) material and silicon (Si) material from a substrate, the vertical stack having the vertically stacked memory cells, the horizontally oriented access devices, and the horizontally oriented storage nodes, and each horizontally oriented access device having gates, channel regions, first source / drain regions, and second source / drain regions separated by the channel regions; forming a first vertical opening through the vertical stack and extending predominantly in a first horizontal direction; sculpting, at least partially, the Si material in the first source / drain region to form a sculpted Si material; and epitaxially growing Si material from the sculpted Si material vertically to form continuous, vertically oriented digit lines in the first vertical opening.

2. The method of claim 1, wherein sculpting the Si material includes removing Si material from exposed, edge surfaces of the Si material perpendicular to an axis extending in the first horizontal direction and perpendicular to an axis extending in a third direction to: reduce a width dimension of the Si material along an axis extending in the first horizontal direction; and reduce a height dimension of the Si material along an axis extending in the third direction.

3. The method of claim 1, wherein the method includes: sculpting the Si material by: recessing a first dielectric material adjacent to the Si material to expose edge surfaces of the Si material; and thinning the exposed edge surfaces using a wet etch process; and epitaxially growing the Si material from the thinned exposed edge surfaces to form the continuous, vertically oriented digit lines.

4. The method of claim 1, wherein forming the first vertical opening further includes: selectively etching the silicon germanium (SiGe) layers and reducing a vertical thickness of the Si layers to form a plurality of first horizontal openings a first length (LI) from the first vertical opening; conformally depositing a second dielectric material on exposed surfaces in the plurality of first horizontal openings; depositing the first dielectric material to fill the plurality of first horizontal openings; selectively etching the second dielectric material from the plurality of first horizontal openings a second length (L2) from the second vertical opening: depositing a first conductive material on the Si layers to form horizontal access lines, serving as gate all around (GAA) structures on a gate dielectric material at the channel regions of the access devices, and separated therefrom by the gate dielectric material; filling the first horizontal openings with the second dielectric material, recessing the second dielectric material to expose edge surfaces of the Si material; thinning the exposed edge surfaces using a wet etch process: and epitaxially growing the Si material from the thinned exposed edge surfaces of the Si material to form the continuous, vertically oriented digit lines.

5. The method of any one of claims 1 to 4, wherein the method includes: forming a plurality of second vertical openings, having a first horizontal direction and a second horizontal direction, through the vertical stack, the second vertical openings extending predominantly in the second horizontal direction to form elongated vertical columns with first vertical sidewalls in the stack, separating memory cells on each level; filling the plurality of second vertical openings with a doped dielectric material (DTI); laterally doping adjacent portions of the Si material in the first horizontal direction;selectively etching doped adj acent portions of the Si material from a first distance from the first vertical opening to expose thinned edge surfaces of Si material: and epitaxially growing the Si material from the exposed thinned edge surfaces to form the continuous, vertically oriented digit lines.

6. The method of any one of claims 1 to 4, wherein the method further includes forming the vertical stack having a plurality of levels where the horizontally oriented storage nodes are located at each level of the plurality of levels to form the arrays of vertically stacked memory cells.

7. The method of any one of claims 1 to 4, wherein the method further comprises: forming the horizontally oriented storage nodes at each level of the vertical stack by: forming a plurality of fourth vertical openings, having the first horizontal direction and a second horizontal direction, through the vertical stack, the fourth vertical openings extending predominantly in the second horizontal direction to form elongated vertical, columns with second vertical sidewalls in the stack; and filling the plurality of fourth vertical openings with a first dielectric material; before forming gate all around (GAA) structures, conformally depositing a second dielectric material on exposed surfaces in the plurality of first horizontal openings; depositing a first dielectric material to fill the plurality of first horizontal openings; selectively etching the second dielectric material from the plurality of first horizontal openings a second length (L2) from the second vertical opening; filling a remaining portion of the first horizontal openings with a first conductive material to a periphery of the vertical stack.

8. A method for forming arrays of vertically’ stacked memory cells, having horizontally oriented access devices and storage nodes, comprising:forming a vertical stack having alternating layers of silicon germanium (SiGe) material and silicon (Si) material from a substrate, the vertical stack having the vertically stacked memoiy cells, the horizontally oriented access devices, and the horizontally oriented storage nodes, and each horizontally oriented access device having gates, channel regions, first source / drain regions, and second source / drain regions separated by the channel regions; forming a first vertical opening at a first region through the vertical stack and extending predominantly in a first horizontal direction; epitaxially growing a first amount of Si material from the first source / drain regions vertically, such that epitaxial growth occurs along a <100> atomic crystalline plane orientation in a third direction, along a <110> atomic crystalline plane orientation in the first horizontal direction, and along a <111> atomic crystalline plane orientation in the second horizontal direction; oxidizing exposed surfaces of the first amount of epitaxially grow n Si material to form oxidized epitaxial Si material wherein oxidizing exposed surfaces occurs at a slower rate on the <100> atomic crystalline plane orientation than an oxidation rate on the <110> atomic crystalline plane orientation and the <111> atomic cry stalline plane orientation; removing the oxidized epitaxial Si material to expose a remaining portion of the epitaxially grown Si material; and epitaxially growing a second amount of Si material from the remaining portion of the epitaxially grow n Si material until the epitaxially growor Si material vertically merges to form continuous, vertically oriented digit lines in the first vertical openings.

9. The method of claim 8, wherein the method includes oxidizing the exposed surfaces of the first amount of epitaxially grown Si material in the first horizontal direction more than in the vertical direction.

10. The method of claim 8, wherein the method includes oxidizing the exposed surfaces of the first amount of epitaxially grow n Si material using a dry oxidation process.

11. The method of claim 8, wherein the method includes oxidizing the exposed surfaces of the first amount of epitaxially grown Si material using a wet oxidation process.

12. The method of claim 8, wherein removing the oxidized epitaxial Si material includes etching the oxidized epitaxial Si material using a wet etch process.

13. The method of any of claims 8 to 12, wherein the method includes converting the continuous, vertically oriented digit lines from the Si material to a conductive material having different conductive characteristics from the Si material by exposing the continuous, vertically oriented digit lines to a tungsten hexafluoride material.

14. A memory device, comprising: an array of vertically stacked memory cells having horizontally oriented access devices, and horizontally oriented storage nodes, wherein: the horizontally oriented access devices include channel regions, first source / drain regions, second source / drain regions separated by the channel regions, and gates on a gate dielectric material; and the horizontally oriented storage nodes are formed horizontally on the second source / drain regions of the horizontally oriented access devices; and a vertical digit line that is epitaxially formed from a sculpted portion of the first source / drain regions of the horizontally oriented access devices.

15. The memory device of claim 14, wherein the array comprises horizontally oriented access lines forming the gates to the horizontally oriented access devices, wherein the horizontally oriented access lines are gate all around (GA A) structures.

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