Source: http://patents.com/us-9870990.html
Timestamp: 2019-01-19 10:05:46
Document Index: 514588026

Matched Legal Cases: ['Application No. 201280026912', 'Application No. 201280026912', 'Application No. 12792601', 'Application No. 2014', 'Application No. 201280026912', 'Application No. 201280026912']

US Patent # 9,870,990. Apparatuses including stair-step structures and methods of forming the same - Patents.com
United States Patent 9,870,990
Freeman , et al. January 16, 2018
Freeman; Eric H. (Kuna, ID), Smith; Michael A. (Boise, ID)
Family ID: 1000003065810
15/288,522
US 20170025348 A1 Jan 26, 2017
14679488 Apr 6, 2015 9466531
14015696 Apr 7, 2015 8999844
13151892 Sep 10, 2013 8530350
Current CPC Class: H01L 23/528 (20130101); H01L 21/31111 (20130101); H01L 21/31144 (20130101); H01L 21/32133 (20130101); H01L 21/32139 (20130101); H01L 21/76838 (20130101); H01L 21/76892 (20130101); H01L 27/11548 (20130101); H01L 27/11556 (20130101); H01L 27/11575 (20130101); H01L 27/11582 (20130101); H01L 2924/0002 (20130101); H01L 2924/0002 (20130101); H01L 2924/00 (20130101)
Current International Class: H01L 29/76 (20060101); H01L 27/11556 (20170101); H01L 27/11548 (20170101); H01L 23/528 (20060101); H01L 27/11575 (20170101); H01L 21/3213 (20060101); H01L 21/311 (20060101); H01L 21/768 (20060101); H01L 27/11582 (20170101)
Field of Search: ;257/319
5707885 January 1998 Lim et al.
7618894 November 2009 Bornstein et al.
8395190 March 2013 Shim
8405142 March 2013 Katsumata et al.
8569829 October 2013 Kiyotoshi
8680604 March 2014 Higashi
8765598 July 2014 Smith et al.
8999844 April 2015 Freeman et al.
9466531 October 2016 Freeman et al.
2009/0310425 December 2009 Sim et al.
2010/0117143 May 2010 Lee et al.
2010/0207186 August 2010 Higashi et al.
2010/0323505 December 2010 Ishikawa et al.
2012/0306089 December 2012 Freeman et al.
2013/0341798 December 2013 Freeman et al.
101647114 Feb 2010 CN
2136398 Dec 2009 EP
2008258458 Oct 2008 JP
2010192589 Sep 2010 JP
2010199311 Sep 2010 JP
2010004047 Jan 2010 WO
Endoh, et al., "Novel Ultrahigh Density Flash Memory with a Stacked Surrounding Gate Transistor (S-SGT) Structured Cell," IEEE Transactions on Electron Devices, vol. 50, No. 4, pp. 945-951 (Apr. 2003). cited by applicant .
Chinese Office Action for Chinese Application No. 201280026912.5, dated Jul. 24, 2015, 18 pages. cited by applicant .
Chinese Second Office Action for Chinese Application No. 201280026912.5, dated Apr. 5, 2016, 20 pages. cited by applicant .
European Office Action for European Application No. 12792601.2, dated Aug. 5, 2015, five (5) pages. cited by applicant .
Fukuzumi, et al., "Optimal Integration and Characteristics of Vertical Array Devices for Ultra High Density, Bit Cost Scalable Flash Memory," IEDM Technical Digest, pp. 449-52 (2007). cited by applicant .
International Search Report for International Application No. PCT/US2012/039215, dated Dec. 26, 2012, 3 pages. cited by applicant .
International Written Opinion for International Application No. PCT/US2012/039215, dated Dec. 26, 2012, 5 pages. cited by applicant .
International Preliminary Report on Patentability for International Application No. PCT/US2012/039215 dated Dec. 2, 2013, 6 pages. cited by applicant .
Japanese Office Action for Japanese Application No. 2014-513577 dated Dec. 2, 2014, 4 pages. cited by applicant .
Supplementary European Search Report and Search Opinion, Application No. EP 12792601.2, issued by the ISA/EP dated Sep. 30, 2014, six (6) pages. cited by applicant .
Chinese Rejection Decision for Chinese Application No. 201280026912.5, dated Oct. 10, 2016, 21 pages. cited by applicant .
Chinese Office Action for Chinese Application No. 201280026912.5, dated Sep. 26, 2017, 4 pages with English translation. cited by applicant.
This application is a continuation of U.S. patent application Ser. No. 14/679,488, filed Apr. 6, 2015, now U.S. Pat. No. 9,466,531, issued Oct. 11, 2016, which is a continuation of U.S. patent application Ser. No. 14/015,696, filed Aug. 30, 2013, now U.S. Pat. No. 8,999,844, issued Apr. 7, 2015, which application is a continuation of U.S. patent application Ser. No. 13/151,892, filed Jun. 2, 2011, now U.S. Pat. No. 8,530,350, issued Sep. 10, 2013, the disclosure of each of which is hereby incorporated herein in its entirety by this reference.
1. A semiconductor structure, comprising: a first stair-step region isolated and vertically offset from a second stair-step region relative to a substrate, wherein each of the first stair-step region and the second stair-step region comprises: a first stair-step structure comprising conductive materials and insulating materials, the first stair-step structure including a first set of contact regions, each contact region of the first set of contact regions vertically offset from other contact regions of the first set of contact regions; a second stair-step structure isolated from the first stair-step structure and comprising the conductive materials and the insulating materials, the second stair-step structure including a second set of contact regions, each contact region of the second set of contact regions vertically offset from other contact regions of the second set of contact regions; and a valley between the first stair-step structure and the second stair-step structure.
2. The semiconductor structure of claim 1, wherein the first stair-step structure and the second stair-step structure of each of the first stair-step region and the second stair-step region face each other to define the valley therebetween.
3. The semiconductor structure of claim 1, wherein the valley of each of the first stair-step region and the second stair-step region is filled with another insulating material.
4. The semiconductor structure of claim 1, wherein each of the first stair-step structure and the second stair-step structure of each of the first stair-step region and the second stair-step region is proximate an array region of the semiconductor structure.
5. The semiconductor structure of claim 1, further comprising a conductive contact electrically connected to each of the conductive materials of the first stair-step structure and each of the conductive materials of the second stair-step structure of each of the first stair-step region and the second stair-step region.
6. The semiconductor structure of claim 1, further comprising conductive contacts extending through an insulating material in the valley to the contact regions of the first stair-step structure and to the contact regions of the second stair-step structure of each of the first stair-step region and the second stair-step region.
7. The semiconductor structure of claim 1, further comprising a third stair-step region and a fourth stair-step region each isolated and vertically offset from the first stair-step region and the second stair-step region.
8. The semiconductor structure of claim 1, wherein the second stair-step structure of each of the first stair-step region and the second stair-step region comprises a mirror image of the first stair-step structure of each of the first stair-step region and the second stair-step region.
9. A semiconductor structure including an overall stair-step structure, the overall stair-step structure comprising: a plurality of stair-step regions, each stair-step region of the plurality of stair-step regions being vertically offset from each other, wherein each stair-step region of the plurality of stair-step regions comprises: a plurality of sets of conductive material and insulating material; a first stair-step structure comprising a first set of contact regions comprising a first portion of sequential sets of the plurality of sets, the first set of contact regions extending in a first direction from a top first contact region to a bottom first contact region; and a second stair-step structure spaced from the first stair-step structure, the second stair-step structure comprising a second set of contact regions comprising a second portion of sequential sets of the plurality of sets, the second set of contact regions extending in the first direction, wherein a top contact region of the second set of contact regions is vertically higher than all of the contact regions of the first set of contact regions, wherein the first stair-step structure and the second stair-step structure of each stair-step region of the plurality of stair-step regions face each other to define a valley therebetween.
10. The semiconductor structure of claim 9, wherein the second stair-step structure is spaced from the first stair-step structure by another insulating material.
11. The semiconductor structure of claim 9, further comprising a third stair-step structure spaced from at least one of the first stair-step structure or the second stair-step structure, the third stair-step structure comprising a third set of contact regions comprising a third portion of sequential sets of the plurality of sets, the contact regions of the third set of contact regions vertically offset from the first set of contact regions and the second set of contact regions.
12. The semiconductor structure of claim 11, further comprising a fourth stair-step structure comprising a fourth set of contact regions comprising a fourth portion of sequential sets of the plurality of sets, the contact regions of the fourth set of contact regions vertically offset from the first set of contact regions, the second set of contact regions, and the third set of contact regions.
13. The semiconductor structure of claim 9, further comprising a respective conductive contact in electrical communication with each contact region of the first set of contact regions and of the second set of contact regions.
14. The semiconductor structure of claim 9, wherein the conductive material comprises a metal.
15. A method of forming a semiconductor structure including at least one stair-step structure, the method comprising: forming a first stair-step region and forming a second stair-step region that is isolated and vertically offset from the first stair-step region, wherein forming each of the first stair-step region and the second stair-step region comprises: forming a plurality of sets of conductive material and insulating material; forming a first stair-step structure comprising a first set of contact regions comprising a first portion of sequential sets of the plurality of sets, the first set of contact regions extending in a first direction from a top first contact region to a bottom first contact region; and forming a second stair-step structure comprising a second set of contact regions spaced from the first set of contact regions and comprising a second portion of sequential sets of the plurality of sets, the second set of contact regions extending in the first direction, wherein a top contact region of the first stair-step structure of the first stair-step region is higher than all of the contact regions of the first stair-step structure of the second stair-step region, wherein the first stair-step structure and the second stair-step structure of each of the first stair-step region and the second stair-step region face each other to define a valley therebetween.
16. The method of claim 15, wherein forming a first set of contact regions comprises: forming a mask over a topmost set of conductive material and insulating material of the plurality of sets of conductive material and insulating material; removing a portion of the mask to expose a portion of the topmost insulating material; and removing at least a portion of the conductive material of the topmost set of conductive material and insulating material.
17. The method of claim 15, wherein forming a first set of contact regions comprises: forming a mask over a first region of the plurality of sets of conductive material and insulating material; and removing some of the sets of the plurality of sets of conductive material and insulating material while the mask remains over the first region.
18. The method of claim 15, wherein forming a second set of contact regions spaced from the first set of contact regions comprises disposing another insulating material between the first set of contact regions and the second set of contact regions.
19. The method of claim 15, wherein forming a second set of contact regions comprises forming a stair-step structure comprising the second portion of sequential sets of the plurality of sets facing a stair-step structure of the first stair-step structure.
20. The method of claim 15, further comprising selecting the conductive material to comprise a metal.
Embodiments of the present disclosure relate to apparatuses such as three-dimensional semiconductor devices and systems including the same. Embodiments of the present disclosure also relate to so-called "stair-step" structures including conductive materials in so-called "stair-step" configurations for electrical connection between, for example, memory cells and conductive lines. Other embodiments of the present disclosure relate to methods for forming stair-step structures and devices including stair-step structures.
Vertical memory arrays and methods of forming them are described in, for example: U.S. Patent Application Publication No. 2007/0252201 of Kito et al., now U.S. Pat. No. 7,936,004, issued May 3, 2011; Tanaka et al., "Bit Cost Scalable Technology with Punch and Plug Process for Ultra High Density Flash Memory," Symposium on VLSI Technology Digest of Technical Papers, pp. 14-15 (2007); Fukuzumi et al., "Optimal Integration and Characteristics of Vertical Array Devices for Ultra-High Density, Bit-Cost Scalable Flash Memory," IEDM Technical Digest, pp. 449-52 (2007); and Endoh et al., "Novel Ultrahigh-Density Flash Memory with a Stacked-Surrounding Gate Transistor (S-SGT) Structured Cell," IEEE Transactions on Electron Devices, vol. 50, no. 4, pp. 945-951 (April, 2003).
Conventional vertical memory arrays require an electrical connection between the conductive materials (e.g., word line plates or control gates) and access lines (e.g., word lines) so that memory cells in the 3-D array may be uniquely selected for writing or reading functions. One method of forming an electrical connection includes forming a so-called "stair-step" structure at the edge of the conductive materials. FIGS. 1A through 1D show one conventional method of creating a stair-step structure 10 in a stack of conductive materials 12. As shown in FIG. 1A, conductive materials 12 are separated by insulating materials 14 between the conductive materials 12. A mask 16 (e.g., photoresist material) is formed over the topmost insulating material 14 and patterned to expose a portion of the insulating material 14a, the exposed portion having a width of one so-called "step" of the stair-step structure 10 to be formed. An anisotropic etch 18, such as a reactive ion etch (RIE) or other dry etch, is performed to remove the insulating material 14a at the portion exposed through the mask 16. The pattern in the insulating material 14a is then transferred to the conductive material 12a. The exposed insulating material 14a is removed by one dry etch process that stops on the conductive material 12a, and the exposed conductive material 12a is then removed by another dry etch process that stops on the insulating material 14b. Next, the mask 16 is reduced in size by removing a portion of the mask (also known as "trimming"), such as by isotropic etching, to expose another portion of the insulating material 14a, as shown in FIG. 1B.
The process is repeated by subjecting the structure to an anisotropic etch 18, including removing exposed portions of the two insulating materials 14a and 14b and subsequently removing exposed portions of the two conductive materials 12a and 12b. As shown in FIG. 1C, the successive reduction in size of the mask 16 and the repeated dry etch processes are continued until the insulating material 14c and conductive material 12c is exposed, the mask 16 is removed, and a stair-step structure 10 remains. Word line contacts 20 are formed to extend through each respective insulating material 14 and electrically contact each conductive material 12, as shown in FIG. 1D. The top of each word line contact 20, as viewed in FIG. 1D, connects to a conductive word line (not shown). While FIGS. 1A through 1D illustrate using two anisotropic etches 18 to create three so-called "steps" of the stair-step structure 10, the acts of etching the insulating material 14, etching the conductive material 12, and trimming the mask 16 may be repeated to create more steps (and thus contact regions for word line contacts). Current conventional methods have been used to form more than eight contact regions (e.g., steps).
FIG. 26 illustrates an embodiment of a stair-step structure facing another stair-step structure with a dielectric in a valley between the facing stair-step structures.
As used herein, the term "apparatus" includes a device, such as a memory device (e.g., a vertical memory device), or a system that includes such a device.
As used herein, the term "substantially" includes to a degree that one skilled in the art would understand the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances.
As used herein, the term "set" includes a conductive material(s) and an immediately adjacent insulating material(s). Each conductive material can form a word line connection separated from additional conductive materials by the insulating material. Each insulating material may insulate (e.g., electrically insulate, separate, isolate from) the conductive material in its set from the conductive material of an adjacent set. The conductive material of each set may form a conductive connection (e.g., a word line connection) for supplying electrical signals to a semiconductor device. Although this disclosure and the accompanying drawings refer to sets that each include an insulating material formed over (e.g., on a side opposite a substrate) a conductive material, this disclosure is not so limited. A set may include a conductive material formed over (e.g., on a side opposite the substrate) an insulating material. The term "set" is used merely for ease in describing, illustrating, and understanding the methods and structures disclosed.
As used herein, any relational term, such as "first," "second," "over," "under," "on," "underlying," "topmost," "next," etc., is used for clarity and convenience in understanding the disclosure and accompanying drawings and does not connote or depend on any specific preference, orientation, or order, except where the context clearly indicates otherwise.
As used herein, the terms "distal" and "proximal" describe positions of materials or features in relation to a substrate upon which the material or feature is formed. For example, the term "distal" refers to a position relatively more distant from the substrate, and the term "proximal" refers to a position in closer relative proximity to the substrate.
As used herein, the terms "lateral" and "laterally" refer to a direction that is parallel to the direction that a "step" (e.g., contact region) of the stair-step structure extends. For example, the lateral direction may be perpendicular to a direction that access lines (e.g., word lines) extend in a vertical memory device including a stair-step structure to be described in more detail below. The lateral direction may also be parallel to a direction that bit lines extend in a vertical memory device including the stair-step structure. For example, the direction indicated by arrows 140 in FIG. 7 is the lateral direction.
Non-volatile memory devices (e.g., vertical memory devices, such as a three-dimensional NAND memory devices) including a plurality of contact regions on so-called "stair-steps" are disclosed, as are methods of forming such devices. A pattern of the contact regions located along an edge of the non-volatile memory device can be formed on so-called "steps" in the non-volatile memory device. A contact may be formed on each contact region to form connections (e.g., electrical connections) to a conductive material (e.g., word line connection or control gate). While the non-volatile memory devices described herein may make specific reference to NAND devices, the disclosure is not so limited and may be applied to other semiconductor and memory devices. Some embodiments of a stair-step structure of the present disclosure and methods of forming such a stair-step structure are shown in FIGS. 2 through 25 and are described hereafter. Similar structures or components in the various drawings may retain the same or similar numbering for the convenience of the reader; however, the similarity in numbering does not mean that the structures or components are necessarily identical in size, composition, configuration, or any other property. Embodiments disclosed herein include stair-step structures (see FIGS. 9, 10, 12, 14, 20) that include at least two regions laterally adjacent each other, each region of the at least two regions providing access to a portion of a plurality of conductive materials. A first region may provide access to a first portion of the plurality of conductive materials. A second region may provide access to a second portion of the plurality of conductive materials different from the first portion. Embodiments disclosed herein also include methods of forming stair-step structures.
An embodiment of a method of forming a stair-step structure 100 for electrical access to a vertical device (e.g., memory array) is illustrated by way of example in FIGS. 2 through 10. Alternating conductive materials 112 and insulating materials 114 may be formed over a substrate (not shown) by conventional methods. The substrate over which the conductive materials 112 and insulating materials 114 are formed may be any substantially planar material. By way of non-limiting example, the substrate may be a semiconductor material and may include at least portions of circuits to which transistors of a memory array may be connected. Each conductive material 112 may be used to form a conductive connection (e.g., word line connection, control gate), although the disclosure is not so limited. Each conductive material 112 may, by way of non-limiting example, be a substantially planar conductive material 112. As used herein, the term "substrate" includes a semiconductor-based material including silicon, silicon-on-insulator (SOI) or silicon-on-sapphire (SOS) technology, doped and undoped silicon, doped and undoped semiconductors, epitaxial layers of silicon supported by a base semiconductor foundation, and other semiconductor structures. When reference is made to a "substrate" in the following description, previous process acts may have been conducted to form regions or junctions in or over the base semiconductor structure or foundation. In addition, the semiconductor need not be silicon-based, but may be based on silicon-germanium, silicon-on-insulator, silicon-on-sapphire, germanium, or gallium arsenide, among others.
The alternating conductive materials 112 and insulating materials 114 may include an array region 122 (e.g., a vertical memory array region) and a stair-step region 124 (i.e., a region that may include a stair-step after further processing) of a vertical memory device. The conductive material 112 may be formed from any suitable conductive material(s). By way of example and not limitation, the conductive material 112 may include one or more of polysilicon and a metal, such as tungsten, nickel, titanium, platinum, aluminum, gold, tungsten nitride, tantalum nitride, titanium nitride, etc. The insulating material 114 may be formed from any suitable insulating material(s). By way of example and not limitation, the insulating material 114 may include a silicon oxide (e.g., SiO.sub.2). Each set 115 of conductive material 112 and insulating material 114 may have a thickness that is approximately 1 .mu.m. Each of the conductive material 112 and insulating material 114 may be formed by conventional techniques, which are not described in detail herein.
A first mask 116 may be formed over the topmost set 115a of conductive material 112a and insulating material 114a. The first mask 116 may be referred to as a stair-step mask, as it is used to form a plurality of steps (e.g., contact regions) in the conductive material 112 and insulating material 114. The first mask 116 may be formed of a photoresist material, for example. The first mask 116 may be patterned, as is known in the art, to remove material from the first mask 116 at an outer edge of the stair-step region 124. The material may be removed from the first mask 116 to expose a portion of a major surface of the topmost insulating material 114a in the stair-step region 124 that has a width 111 of approximately a desired width of the step to be formed. By way of example, a final stair-step structure (described in more detail below) to be formed by this method may include individual steps, each exhibiting a width 111 sufficient to provide space for a conductive contact to be formed thereon. For example, the desired width of a step may be in a range of from about 100 nm to about 500 nm. Therefore, the width 111 may be from about 100 nm to about 500 nm. In some embodiments, the width 111 may be from about 220 nm to about 250 nm. However, these particular widths are described by way of example only, and not limitation. The width 111 may be greater or less than the particular widths described.
As used herein, the phrase "to expose" includes to uncover a major surface of a material. For example, the insulating material 114a shown in FIG. 2 includes a portion of a major surface thereof that is exposed.
After the first mask 116 is patterned, the portion of the insulating material 114a exposed through the first mask 116 may be removed by, for example, an anisotropic etch 118. By way of example, the anisotropic etch 118 may include a first dry etch act that removes the exposed portion of the insulating material 114a and exposes the conductive material 112a, followed by a second dry etch act that removes a portion of the conductive material 112a that was exposed by the first dry etch act. The second dry etch act of the anisotropic etch 118 may expose the insulating material 114b. One instance of the first dry etch act and the second dry etch act may be referred to herein as a cycle of the anisotropic etch 118. Since the first dry etch act and the second dry etch act remove the portion of the insulating material 114a and the portion of the conductive material 112a, the first dry etch act and the second dry etch act may remove a portion of the first set 115a. Although the method described herein refers to an anisotropic etch 118, the disclosure is not so limited. For example, an isotropic etch may be used in place of the anisotropic etch 118.
A portion of the first mask 116 may then be removed to expose another portion of the first insulating material 114a, resulting in the structure shown in FIG. 3. The portion of the first mask 116 may be removed by, for example, an isotropic etch that is selective to the material of the first mask 116 and that does not substantially remove the material of the insulating material 114 or the conductive material 112. Material from the first mask 116 may be removed to the extent that the portion of the first insulating material 114a that is exposed exhibits a width that is approximately a desired width of a step, as described above.
Another anisotropic etch 118 may be used to remove exposed portions of the insulating materials 114a and 114b and subsequently exposed portions of the conductive materials 112a and 112b thereunder. In other words, exposed portions of the set 115a and the set 115b may be removed by one cycle of the anisotropic etch 118. A portion of the first mask 116 may be removed again to expose yet another portion of the insulating material 114a, resulting in the structure shown in FIG. 4.
The acts of removing a portion of the first mask 116, removing the exposed insulating material 114, and removing the exposed conductive material 112 may be repeated a plurality of times to expose insulating material 114j and form steps in sets 115a through 115i, which covers one-half of the total number of sets 115, as shown in FIG. 5. In other words and by way of example, where the total number of sets 115 is eighteen, the ninth insulating material 114i (when counting sequentially starting with insulating material 114a) may have an exposed step formed therein, while the tenth insulating material 114j thereunder may not have a step formed therein. The tenth insulating material 114j may have a portion thereof exposed. The remainder of the first mask 116 may then be removed by conventional techniques, which are not described in detail herein. By way of example, the first mask 116 may be substantially removed from the surface of the first insulating material 114a with a dry or wet etch act.
Referring now to FIG. 7, a second mask 126 (also referred to as a "chop mask 126") may be formed over the insulating materials 114a through 114i and patterned to cover the array region 122 (not shown in FIG. 7) and a first region 170 of the stair-step region 124, while leaving a second region 180 of the stair-step region 124 exposed. The second region 180 may be a region that is laterally (i.e., in the direction of the arrows 140 in FIG. 7) adjacent the first region 170. By way of example, the second region 180 may have a length 182 determined by the configuration and size of word lines that will eventually connect to the stair-step structure 100 by way of word line contacts. In an embodiment where each set 115 has a thickness of about 1 .mu.m, the length 182 exposed through the mask 126 may be about 3 .mu.m.
As can be seen in FIG. 9, the second mask 126 may be removed, providing access (i.e., exposure) to each set 115 and forming a stair-step structure 100. The stair-step structure 100 may include a first region 170 providing exposure to a first half of the sets 115 and a second region 180 laterally adjacent the first region 170 providing exposure to a second half of the sets 115. Thus, each set 115 may be accessible to form a conductive contact thereon electrically connected to each conductive material 112, respectively. In other words, an exposed portion of each set 115 may be referred to as a "contact region." Each contact region may be offset from other contact regions. As used herein, the term "offset" includes located at a different distance from a substrate. For example, a first contact region offset from a second contact region may refer to the contact region of a first set and the contact region of a second set different from the first set, as shown in FIG. 9. The contact regions of the stair-step structure 100 may extend at an angle 190 from the substrate, as will be explained in more detail below.
Alternatively, the conductive contacts 120 may be formed to have a configuration different than that shown in FIG. 10. By way of example, the conductive contacts 120 may be formed to extend from each conductive material 112 through the stair-step structure 100 to the substrate rather than or in addition to away from the substrate. For example, U.S. patent application Ser. No. 13/151,945, filed Jun. 2, 2011, now U.S. Pat. No. 8,765,598, issued Jul. 1, 2014, and assigned to the Assignee of the present application, describes contacts extending toward the substrate through a stair-step structure and methods of forming such contacts. In other words, this disclosure is not limited to forming contacts extending from the materials of the stair-step structure 100 in a direction away from the substrate, as shown in FIG. 10.
Another embodiment of a method for forming a stair-step structure is illustrated in FIGS. 11 through 14. The method may begin in a similar fashion to that illustrated in FIGS. 2 through 6 to form an intermediate stair-step structure 250. However, the intermediate stair-step structure 250 of this embodiment is different than the intermediate stair-step structure 150 shown in FIG. 6 because the intermediate stair-step structure 250 includes exposure of, and steps formed in, one-fourth of sets 215 of insulating material 214 and conductive material 212, rather than one-half of the sets 115 as in the intermediate stair-step structure 150 shown in FIG. 6. By way of non-limiting example and for ease of illustration, the structure shown in FIG. 11 includes sixteen total sets 215. However, any desired number of sets 215 may be used. Steps may be formed into the four topmost sets 215 (i.e., one-fourth of the sixteen total sets 215) essentially as described above with reference to FIGS. 2 through 6 to expose the insulating material 214 of each of the four topmost sets 215. A second mask 236 may be formed over the insulating materials 214a through 214d and patterned to expose the sets in a second region 260 laterally adjacent a first region 240 of the intermediate stair-step structure 250.
An anisotropic etch 238 may be performed including four cycles of removing insulating material 214 and conductive material 212 to expose and form steps in the next four sets 215 (215e through 215h) in the exposed second region 260, as illustrated in FIGS. 11 and 12. After the anisotropic etch 238 is performed, the second mask 236 may be removed. Thus, the four topmost sets 215a through 215d may be exposed and have steps formed therein in a first region 240 and the next four sets 215e through 215h may be exposed and have steps formed therein in a second region 260 laterally adjacent the first region 240. The bottom half of the sets 215 (i.e., the eight sets 215 below the eighth set 215h in FIG. 12) may not have steps formed therein. The conductive material 214i of the ninth set 215i may have a portion thereof exposed after the formation of a step in the eighth set 215h.
Referring now to FIG. 13, a third mask 246 may be formed over exposed insulating material 214a through 214d of a first portion 241 of the first region 240 (FIG. 12) and over exposed insulating material 214e through 214h of a first portion 261 of the second region 260 (FIG. 12) and patterned to expose a second portion 243 of the first region 240 and a second portion 263 of the second region 260. By way of non-limiting example, about one-half of each of the first region 240 and of the second region 260 may be covered by the third mask 246 while the remaining about one-half may be exposed.
Another embodiment of a method of forming a stair-step structure for electrical access to a vertical device (e.g., memory array) is illustrated by way of example in FIGS. 15 through 20. Referring to FIG. 15, a number of sets 315 of alternating conductive material 312 and insulating material 314 may be formed. By way of example and for clarity, eighteen sets 315 are shown, although the disclosure is not so limited. A first mask 316 (also referred to as a "stair-step mask 316") may be formed over insulating material 314a to cover both an array region 322 (e.g., a vertical memory array region) and a stair-step region 324. The first mask 316 may be patterned to expose a portion of the insulating material 314a with a width about the same width as a desired step of a stair-step structure to be formed, essentially as described above with reference to FIG. 2.
An anisotropic etch 318 may be performed to remove a portion of the two uppermost sets 315a and 315b. In other words, the anisotropic etch 318 may remove the exposed portion of the insulating material 314a, the underlying portion of the conductive material 312a, the underlying portion of the next insulating material 314b, and the underlying portion of the next conductive material 312b. In other words, two cycles of the anisotropic etch 318 may be performed to remove portions of two sets 315 of conductive material 312 and insulating material 314, rather than one cycle of anisotropic etching 318 through one set 315. A portion of the first mask 316 may then be removed to expose another portion of the insulating material 314a, essentially as described above with reference to FIG. 2.
Referring now to FIG. 16, a portion having a width of about one desired step width of the insulating material 314a may be exposed as well as a similar portion of the third insulating material 314c. Another anisotropic etch 318 may be performed, again etching through two sets 315 of conductive material 312 and insulating material 314. Another portion of the first mask 316 may be removed through an isotropic etch, resulting in the structure shown in FIG. 17. The sequential anisotropic etching 318 and removal of portions of the first mask 316 may continue until steps have been formed in a desired fraction, such as one-half, of the sets 315 and an intermediate stair-step structure 350 is formed, as shown in FIG. 18. In other words, every other set 315 (when proceeding from a substrate towards a topmost set 315a) may have at least a portion of its insulating material 314 exposed, the exposed portion having a width sufficient to form a conductive contact thereon or therethrough.
Referring now to FIG. 19, a second mask 326 (also referred to as a "chop mask 326") may be formed over the exposed insulating materials 314 and patterned to cover a first region 370 of the stair-step region 324 and to expose a second region 380 laterally adjacent the first region 370. One cycle of another anisotropic etch 328 may be performed on the exposed second region 380 to remove an exposed portion of one set 315 from each step. In other words, the anisotropic etch 328 may remove exposed insulating material 314 from each of the exposed sets 315 and then may remove underlying conductive material 312 from each of the exposed sets 315. In this manner, the sets 315 that were not exposed in the intermediate stair-step structure 350 shown in FIG. 18 may be exposed by performing one cycle of the anisotropic etch 328.
An angle 390 of a stair-step structure 300 formed by the method illustrated in FIGS. 15 through 20 may be less than an angle 190 of a stair-step structure 100 formed by the method illustrated in FIGS. 2 through 10. A device including a stair-step structure 300 may also include another stair-step structure facing the first. For example, FIG. 26 illustrates the stair-step structure 350 of FIG. 18 facing another stair-step structure 350. A steeper stair-step structure (i.e., a smaller angle) may result in a valley between neighboring stair-step structures with less width than a valley between stair-step structures that are less steep (i.e., having a larger angle). A valley 304 having such a smaller width may be easier, and therefore cheaper, to fill with dielectric 302 or other desired materials. The valley 304 with a smaller width filled with the dielectric 302 or other desired material may also be easier to planarize, such as before forming contacts providing electrical connection to the conductive materials of the stair-step structure.
Another embodiment of a method for forming a stair-step structure, such as the stair-step structure 300 shown in FIG. 20, is illustrated in FIGS. 21 through 24. As shown in FIG. 21, alternating conductive materials 412 and insulating materials 414 may be formed over a substrate (not shown) to form a plurality of sets 415, each set 415 including one or more conductive material(s) 412 and one or more insulating material(s) 414. By way of example and not limitation, eighteen sets 415 are shown for clarity, although the disclosure is not so limited. A first mask 426 (also referred to as a "chop mask 426") may be formed over the insulating material 414a and patterned to expose the insulating material 414a in a second region 480 laterally adjacent a first region 470. The first mask 426 may also be formed to cover an array region (not shown). Material from the set 415a including the insulating material 414a and the conductive material 412a may be removed in the second region 480 by a cycle of an anisotropic etch 428.
As shown in FIG. 22, the set 415a may remain in the first region 470 and be removed in the second region 480, exposing the insulating material 414b in the second region 480. The first mask 426 may be removed from the first region 470 to expose the insulating material 414a in the first region 470. Referring now to FIG. 23, a second mask 436 (also referred to as a "stair-step mask 436") may be formed over both the first region 470 and the second region 480 and patterned to expose approximately one stair-width of the insulating materials 414a and 414b. Material from the two sets 415a and 415b may be removed by an anisotropic etch 438 in the first region 470 and material from the two sets 415b and 415c may be removed by the anisotropic etch 438 in the second region 480. In other words, the anisotropic etch 438 may include two cycles of etching through insulating material 414 and conductive material 412. A portion of the second mask 436 may then be removed to expose a portion of the two sets 415a and 415b having a width of approximately one stair-width, as illustrated in FIG. 24.
In the first region 470, portions of the insulating material 414a and portions of the insulating material 414c may be exposed. In the second region 480 laterally adjacent the first region 470, portions of the second insulating material 414b and the fourth insulating material 414d may be exposed. Another anisotropic etch 438 may be performed to remove exposed portions of the sets 415a, 415b, 415c, and 415d, again removing two sets 415 in each exposed portion.
In some embodiments, multiple stair-step structures 100, 200, or 300 may be formed simultaneously following the methods described herein, as will be appreciated by one skilled in the art. By way of example and as illustrated in FIG. 25, a first stair-step structure 100a may be formed as described in more detail hereinabove to include a first region 170a and a second region 180a laterally adjacent the first region 170a. At the same time and by following the same methods, a second stair-step structure 100b may be formed laterally adjacent the first stair-step structure 100a. For example, a first region 170b of the second stair-step structure 100b may be formed laterally adjacent the second region 180a of the first stair-step structure 100a. The first stair-step structure 100a may be electrically insulated from the second stair-step structure 100b by way of an insulating material (not shown), which could be a void, disposed between the first and second stair-step structures 100a and 100b.
Previous Patent US 9,870,989 | Next Patent US 9,870,991