阅读说明：本技术 一种虚拟沟道孔的制备方法及三维存储器 (Preparation method of virtual channel hole and three-dimensional memory ) 是由 李贝贝 许宗珂 袁彬 王同 张强威 于 2021-01-05 设计创作，主要内容包括：本发明公开一种虚拟沟道孔的制备方法及三维存储器,所述制备方法包括以下步骤：提供一衬底,所述衬底上设有多个芯片单元,相邻所述芯片单元之间设有切割道区,所述切割道区内设有一图形对准区；间隔不同预设距离刻蚀衬底,在所述图形对准区形成多个开口；移除所述图形对准区表面的顶层叠置层,暴露所述第五叠置层；在所述多个开口及所述第五叠置层表面沉积隔离材料,形成隔离材料层；平坦化处理所述隔离材料层及所述第五叠置层,使剩余所述隔离材料层与所述第四叠置层表面平齐；移除所述第四叠置层,获得多组规则排列的沟槽,用来供所述虚拟沟道孔对准。本发明解决了虚拟沟道孔制备步骤冗长,制造成本高且对准精度差的问题。(The invention discloses a preparation method of a virtual channel hole and a three-dimensional memory, wherein the preparation method comprises the following steps: providing a substrate, wherein a plurality of chip units are arranged on the substrate, a cutting channel area is arranged between every two adjacent chip units, and a graph alignment area is arranged in the cutting channel area; etching the substrate at different preset distances, and forming a plurality of openings in the pattern alignment area; removing the top superposed layer on the surface of the pattern alignment area to expose the fifth superposed layer; depositing an isolation material on the plurality of openings and the surface of the fifth superposed layer to form an isolation material layer; planarizing the isolation material layer and the fifth superposed layer to enable the rest of the isolation material layer to be flush with the surface of the fourth superposed layer; and removing the fourth stacked layer to obtain a plurality of groups of regularly arranged grooves for aligning the virtual channel holes. The invention solves the problems of long preparation steps of the virtual channel hole, high manufacturing cost and poor alignment precision.)

1. A preparation method of a virtual channel hole is characterized by comprising the following steps:

providing a substrate, wherein a plurality of chip units are arranged on the substrate, a cutting channel area is arranged between every two adjacent chip units, and a graph alignment area is arranged in the cutting channel area;

the substrate comprises a first superposed layer, a second superposed layer, a third superposed layer, a fourth superposed layer and a fifth superposed layer which are arranged in a laminated manner, wherein the surface of the fifth superposed layer is provided with a top superposed layer;

etching downwards along the top layer stack layer to the surface of the first stack layer at different preset distances, and forming a plurality of openings in the pattern alignment area;

removing the top superposed layer on the surface of the pattern alignment area to expose the fifth superposed layer;

depositing an isolation material layer on the plurality of openings and the surface of the fifth superposed layer;

planarizing the isolation material layer and the fifth superposed layer in the pattern alignment area to enable the rest isolation material layer to be flush with the surface of the fourth superposed layer;

and removing the fourth superposed layer to obtain a plurality of groups of regularly arranged grooves as alignment marks for aligning the virtual channel holes.

2. The method of claim 1, wherein the first, second, third, fourth and fifth stacked layers have different thicknesses.

3. The method of claim 1, wherein the width of the trench is equal to the width of the virtual channel hole to be aligned.

4. The method of claim 1, wherein the thickness of the fourth stacked layer is not less than 270 nm.

5. The method of claim 1, wherein the pattern alignment area is a square.

6. The method of claim 1, wherein the alignment mark comprises a plurality of sets of alignment marks in the pattern alignment region.

7. The method of claim 1, wherein the position of the trench formed in the pattern alignment region corresponds to the position of the virtual channel hole in the chip unit.

8. The method of claim 1, wherein the step of forming the plurality of trenches in the pattern alignment region is performed simultaneously with the etching process in the chip unit.

9. The method of claim 8, wherein a mask pattern required for forming the plurality of openings is disposed on the mask for etching the chip unit at positions corresponding to the scribe lines.

10. A three-dimensional memory obtained by the method for preparing a virtual channel hole according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of three-dimensional memories, and particularly relates to a preparation method of a virtual channel hole and a three-dimensional memory.

Background

The three-dimensional memory solves the limitation caused by a two-dimensional or planar flash memory by vertically stacking a plurality of layers of data storage units, supports the accommodation of higher storage capacity in a smaller space, and further effectively reduces the cost and the energy consumption. The control gate of the related art three-dimensional memory is generally formed through a gate last process. The gate-last process is a process in which the stack layer formed initially includes a plurality of sacrificial layers arranged at intervals, the sacrificial layers are removed in the subsequent process, and the original space of the sacrificial layers is filled with an electrode medium (such as metal or polysilicon). In the process of forming a control gate of a three-dimensional memory by using a gate last process, when a sacrificial layer is removed and a gate dielectric is not filled, the whole device is supported by a Channel Hole (CH), but as the number of data storage units vertically stacked in height of the conventional three-dimensional memory increases and as the size of a channel through hole is gradually reduced, the support force of the CH after the sacrificial layer is removed is insufficient, which easily causes the collapse of the whole structure and causes loss. In order to solve the problem of collapse of the whole structure after the sacrificial layer is removed, a virtual channel hole (DCH) for supporting is created. In the related art, the DCH and the CH only function differently, and the manufacturing processes of the DCH and the CH are completely the same, and the structures are also completely the same. The etching of the virtual channel hole uses a hard mask made of opaque material at present, and because the hard mask is opaque, for the purpose of aligning the virtual channel hole, a plurality of process steps are usually added before the preparation of the virtual channel hole, and an alignment mark is made for the etching of the virtual channel hole, so that the whole preparation process is long. In addition, in the prior art, the manufacturing process of the virtual channel hole and the channel hole needs to share the same alignment photomask, which also causes the problems of high alignment difficulty, inaccurate alignment and the like.

Disclosure of Invention

The invention aims to provide a preparation method of a virtual channel hole and a three-dimensional memory, and solves the problems of long preparation process steps, high manufacturing cost and poor alignment precision of the original virtual channel hole.

In order to solve the technical problems, the invention is realized by the following technical scheme:

the invention provides a preparation method of a virtual channel hole, which at least comprises the following steps:

providing a substrate, wherein a plurality of chip units are arranged on the substrate, a cutting channel area is arranged between every two adjacent chip units, and a graph alignment area is arranged in the cutting channel area;

the substrate comprises a first superposed layer, a second superposed layer, a third superposed layer, a fourth superposed layer and a fifth superposed layer which are arranged in a laminated manner, wherein the surface of the fifth superposed layer is provided with a top superposed layer;

etching downwards along the top layer superposed layer at different preset distances until the surface of the first superposed layer stops, and forming a plurality of openings in the pattern alignment area;

removing the top superposed layer on the surface of the pattern alignment area to expose the fifth superposed layer;

depositing an isolation material layer on the plurality of openings and the surface of the fifth superposed layer;

planarizing the isolation material layer and the fifth superposed layer in the pattern alignment area to enable the rest isolation material layer to be flush with the surface of the fourth superposed layer;

and removing the fourth stacked layer to obtain a plurality of groups of regularly arranged grooves for aligning the virtual channel holes.

In one embodiment of the invention, the thicknesses of the first, second, third, fourth and fifth superposed layers are different.

In one embodiment of the present invention, the width of the trench is equal to the width of the virtual channel hole.

In one embodiment of the invention, the thickness of the fourth stacked layer is not less than 270 nm.

In one embodiment of the invention, the graphic alignment area is in a shape of a Chinese character 'hui'.

In one embodiment of the present invention, a plurality of sets of the alignment marks are included in the pattern alignment area.

In an embodiment of the invention, the position of the trench formed in the pattern alignment region corresponds to the position of the dummy trench hole in the chip unit.

In one embodiment of the present invention, the material used for the isolation material layer is tetraethoxysilane.

In one embodiment of the present invention, the process step of forming a plurality of trenches in the pattern alignment region is performed simultaneously with the etching process in the chip unit.

In one embodiment of the present invention, a mask pattern required for preparing a plurality of trenches is disposed at a position corresponding to the scribe line of the mask used for etching the chip unit.

The invention also provides a three-dimensional memory, which is obtained by adopting the preparation method of the virtual channel hole.

The alignment mark photomask is independently manufactured for etching the virtual channel hole on the existing substrate, so that the etching of the virtual channel hole does not need to share the alignment photomask with the etching of the channel hole, the etching of the virtual channel hole can be more accurately aligned, and the alignment precision is improved.

Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow chart of a method of fabricating a dummy trench hole according to the present invention;

FIG. 2 is a schematic diagram of the alignment mark structure of the virtual channel hole of the present invention;

FIG. 3 is a schematic view of the substrate structure of FIG. 1;

fig. 4 and 5 are schematic views corresponding to step S3 in fig. 1;

FIG. 6 is a schematic diagram corresponding to step S4 in FIG. 1;

FIG. 7 is a diagram corresponding to step S5 in FIG. 1;

fig. 8 and 9 are schematic views corresponding to step S6 in fig. 1;

FIG. 10 is a diagram corresponding to step S7 in FIG. 1;

FIG. 11 is an electron microscope image of a virtual via alignment mark of the present invention;

FIG. 12 is an electron micrograph of a trench in a dummy via alignment mark according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The three-dimensional memory solves the limitation caused by a two-dimensional or planar flash memory by vertically stacking a plurality of layers of data storage units, supports the accommodation of higher storage capacity in a smaller space, further effectively reduces the cost and the energy consumption, plays a role in supporting a virtual channel hole (DCH, DummyChannelHole) in the three-dimensional memory, and prevents the collapse of the whole structure after a sacrificial layer is removed. With higher and higher integration, three-dimensional memories have evolved from 32 layers to 64 layers and even higher, which require exposure of several or even tens of layers of mask patterns on a wafer to form complete circuit structures. Each lithography requires precise alignment of the reticle used for that lithography with the exposed first layer pattern or the previous layer or layers of patterns on the wafer prior to exposure. The control of the alignment accuracy of lithography determines the complexity and functional density of integrated circuits. Therefore, alignment precision of alignment is required to be ensured between different layers of patterns, in the process of forming the virtual channel hole, for the purpose of aligning the virtual channel hole, a plurality of process steps are added before the virtual channel hole is prepared, and an alignment mark is prepared for etching the virtual channel hole, so that the whole preparation process is long. In addition, if the same alignment mask is used in the manufacturing process of the virtual channel hole and the channel hole, the problems of high alignment difficulty, inaccurate alignment and the like are also caused. Specifically, the alignment of the virtual channel hole and the alignment of the channel hole share one photomask, so that the alignment of the virtual channel hole can only be partially aligned, which makes the alignment accuracy difficult to guarantee.

It is worth mentioning that the depth of the alignment mark required in the process of forming the virtual channel hole is, for example, -2500 +/-250A, and the thickness interval of the fourth stacked layer of the substrate in the invention is within this range, and the fourth stacked layer is also removed in the final integrated circuit preparation, so the invention considers that an alignment mark pattern specially used for the virtual channel hole is manufactured in the dicing channel region of the substrate, and after the process of removing the topmost nitride in the conventional manufacturing process of the integrated circuit, the alignment mark pattern formed in the dicing channel region is naturally formed and used for alignment in the subsequent etching process of the virtual channel hole, and the process does not need to add a process step of separately manufacturing a virtual channel hole alignment mask, thereby greatly saving the whole manufacturing cost, and greatly reducing the whole manufacturing cost.

Referring to fig. 1, the present invention provides a method for preparing a virtual channel hole, including the following steps:

s1, providing a substrate 100, wherein a plurality of chip units are arranged on the substrate 100, a cutting channel area is arranged between every two adjacent chip units, and a graph alignment area 200 is arranged in each cutting channel area;

s2, the substrate 100 comprises a first superposed layer 101, a second superposed layer 102, a third superposed layer 103, a fourth superposed layer 104 and a fifth superposed layer 105 which are arranged in a laminated mode, wherein a top-layer superposed layer 106 is arranged on the surface of the fifth superposed layer 105;

s3, etching downwards along the top layer 106 at different preset distances until the surface of the first superposed layer 101 stops, and forming a plurality of openings in the pattern alignment area 200;

s4, removing the top layer stacking layer 106 on the surface of the graph alignment area 200 and exposing the fifth stacking layer 105;

s5, depositing an isolation material layer 107 on the plurality of openings and the surface of the fifth stacking layer 105;

s6, flattening the isolation material layer 107 and the fifth superposed layer 105 in the graph alignment region 200 to enable the residual isolation material layer 107 to be flush with the surface of the fourth superposed layer 104;

s7, removing the fourth stacked layer 104 to obtain a plurality of groups of regularly arranged trenches 300 for aligning the dummy trench holes.

Referring to fig. 1 and 3, in step S1, a substrate 100 is provided, a plurality of chip units are disposed on the substrate 100, a scribe line region is disposed between adjacent chip units, a pattern alignment region 200 is disposed in the scribe line region, the pattern alignment region 200 is in a shape of a Chinese character 'hui', and a plurality of sets of alignment mark patterns may be included in the graphic alignment region 200 in the shape of a Chinese character 'hui'. The material of the substrate 100 may include, but is not limited to, single crystal or polycrystalline semiconductor material, and the substrate 100 may also include an intrinsic single crystal silicon substrate 100 or a doped silicon substrate 100. The substrate 100 includes a substrate 100 of a first doping type, which may be a P-type substrate or an N-type substrate, and in this embodiment, only the first doping type is a P-type substrate, that is, in this embodiment, the substrate 100 only exemplifies a P-type substrate 100, for example, a P-type silicon substrate 100. In some embodiments, the substrate 100 may also be a single crystal silicon substrate 100, a Ge substrate 100, a SiGe substrate 100, a Silicon On Insulator (SOI), or any combination thereof, and an appropriate semiconductor material may be selected as the substrate 100 according to the actual requirements of the device, which is not limited herein. In some embodiments, the substrate 100 may also be composed of a compound semiconductor material, such as a III-V semiconductor material or a II-VI semiconductor material. In this embodiment, the chip units are, for example, bare chips, and a dicing street region is provided between adjacent bare chips to separate the bare chips.

Referring to fig. 1 and 3, in step S2, the substrate 100 includes a first stacked layer 101, a second stacked layer 102, a third stacked layer 103, a fourth stacked layer 104, and a fifth stacked layer 105, which are stacked, and a top stacked layer 106 is disposed on a surface of the fifth stacked layer 105. Wherein the first stacked layer 101 is for example an oxide layer, the second stacked layer 102 is for example a nitride layer, the third stacked layer 103 is for example an oxide layer, the fourth stacked layer 104 is for example a nitride layer, the fifth stacked layer 105 is for example an oxide layer, and the top stacked layer 106 is for example a metal oxide layer. The thicknesses of the first stacked layer 101, the second stacked layer 102, the third stacked layer 103, the fourth stacked layer 104 and the fifth stacked layer 105 are different, and the specific thickness value can be set according to the requirements of the integrated circuit product, in this embodiment, the thickness of the fourth stacked layer 104 is not less than 270nm, for example, in a range of 2500+/-250A, in addition, the thickness of the second stacked layer 102 is, for example, 320A, the thickness of the third stacked layer 103 is, for example, 2200A, the thickness of the fourth stacked layer 104 is, for example, 2700A, the thickness of the fifth stacked layer 105 is, for example, 180A, and the thickness of the top stacked layer 106 is, for example, 1200A.

Referring to fig. 2, 4 and 5, in step S3, a method for preparing a plurality of sets of alignment mark patterns in the reverse-type pattern alignment area 200 includes: etching down to the surface of the first stack layer 101 along the top stack layer 106 at different predetermined distances to form a plurality of openings. This process may be performed simultaneously with the etching process in the chip unit, and no additional process step is required, specifically, a mask pattern required for preparing a plurality of openings may be disposed at the position of the corresponding scribe line of the mask used for etching the chip unit, in this embodiment, the opening etching may be performed, for example, by using a reactive ion etching or plasma etching process, that is, the top stacked layer 106, the fifth stacked layer 105, the fourth stacked layer 104, the third stacked layer 103, and the second stacked layer 102 are sequentially etched by using the reactive ion etching or plasma etching process until the etching of the surface of the first stacked layer 101 is stopped, so as to form a plurality of openings. More specifically, in some embodiments, a photoresist layer may be formed on the top stacked layer 106, for example, by using a spin coating method, an exposure and development process is performed to form an opening pattern on the photoresist layer, so as to obtain a first patterned photoresist layer 108, the top stacked layer 106, the fifth stacked layer 105, the fourth stacked layer 104, the third stacked layer 103, and the second stacked layer 102 under the opening pattern are removed with the first patterned photoresist layer 108 as a mask until etching of the surface of the first stacked layer 101 stops, and then the photoresist layer may be removed by using a wet cleaning method.

Referring to fig. 4 and 5, in some embodiments, a photoresist layer, which may be a positive photoresist or a negative photoresist, is coated on the substrate 100, the photoresist layer covers the chip unit and also covers the pattern alignment area 200 in the scribe line area, a mask is disposed on the photoresist layer, the mask includes a pattern corresponding to the opening of the pattern alignment area 200 and a mask pattern required for etching the chip unit, the substrate 100 coated with the photoresist layer is exposed, the characteristics of the photoresist layer are changed after exposure, the light-sensitive portion of the positive photoresist is easily dissolved, and the negative photoresist is opposite. The substrate 100 is then developed, the positive photoresist is developed and dissolved, leaving only the unexposed portions, and if the negative photoresist is used, the exposed portions become less soluble, leaving the exposed portions after development. And then etching the substrate 100, forming an opening on the substrate 100 corresponding to the cutting path region, forming an etching structure required by the chip unit forming process, and finally removing the residual photoresist. At this time, the opening structure formed in the pattern alignment region 200 is formed in the scribe line region, so that there is no influence on the subsequent processing of the chip unit, and the formed opening can be covered by the shielding material during the subsequent etching process of the chip unit, thereby avoiding exposure.

Referring to fig. 6, in step S4, the top stack layer 106 on the surface of the pattern alignment area 200 is removed to expose the fifth stack layer 105. The top stack layer 106 may be removed by wet etching or dry etching, for example, in this embodiment, the top stack layer 106 is removed by concentrated sulfuric acid to expose the fifth stack layer 105, and this process may be performed simultaneously with the etching process of the chip unit region, so as to achieve the purpose of saving the overall process steps.

Referring to fig. 7, 8 and 9, in steps S5 and S6, a spacer material layer 107 is deposited on the plurality of openings and the surface of the fifth stacked layer 105. In this embodiment, the isolation material layer 107 is, for example, tetraethoxysilane, and in this embodiment, tetraethoxysilane is deposited on the surfaces of the plurality of openings and the fifth stacked layer 105 by, for example, a high-density plasma chemical vapor deposition method to fill the openings, and then the isolation material layer 107 and the fifth stacked layer 105 are planarized by, for example, chemical mechanical polishing, so that the isolation material layer 107 is flush with the surface of the fourth stacked layer 104. The process can be carried out simultaneously with the etching process of the chip unit area, so as to achieve the purpose of saving the whole process steps.

Referring to fig. 10, 11 and 12, in step S7, the fourth stacked layer 104 is removed to obtain a plurality of regularly arranged trenches 300 as alignment marks for aligning the dummy channel holes, wherein the positions of the trenches 300 correspond to the positions of the dummy channel holes in the chip unit, so as to achieve the purpose of aligning the dummy channel holes. In the present embodiment, the width of the trench 300 is 2600nm, for example, and the depth of the trench 300 is 270nm, for example. Specifically, in some embodiments, a photoresist layer may be formed on the surfaces of the fourth stacked layer 104 and the isolation material layer 107 by, for example, a spin coating method, an exposure and development process is performed to form an opening on the photoresist layer, the opening corresponds to the position of the fourth stacked layer 104, a second patterned photoresist layer is obtained, the fourth stacked layer 104 under the opening pattern is removed by using the second patterned photoresist layer as a mask until the etching on the surface of the third stacked layer 103 is stopped, and then the remaining photoresist layer may be removed by a wet cleaning process, so that a plurality of sets of regularly arranged trenches 300 are obtained as alignment marks for aligning the dummy trench holes. The widths of the plurality of groups of regularly arranged grooves 300 obtained by the method can completely correspond to the width of the virtual channel hole, so that the purpose of serving as the alignment mark of the virtual channel hole is achieved.

The method separately makes the alignment mark for etching the virtual channel hole on the substrate 100, the alignment mark is formed by a plurality of groups of regularly arranged grooves 300, so that the etching of the virtual channel hole does not need to share an alignment photomask with the etching of the channel hole, the etching of the virtual channel hole can be more accurately aligned, and the alignment precision is improved.

The invention also provides a three-dimensional memory, which is obtained by adopting the preparation method of the virtual channel hole.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above disclosure of selected embodiments of the invention is intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.