Patent Description:
The disclosure relates to the field of a semiconductor, and specifically to a word line lead-out structure and a method for preparing of a bit word lead-out structure.

A semiconductor memory uses a transistor array to control the charging and discharging of a storage capacitor to realize data access. A gate of the transistor is electrically connected with a word line. After the word line is formed in a substrate, a word line lead-out structure needs to be formed above the word line to reach an electric connection between the word line and an external control circuit.

However, with the continuous improvement of the integration level of a semiconductor device, the size of a word line and the space between word lines are increasingly reduced; correspondingly, the area of the word line lead-out structure is increasingly reduced. As a result, the contact resistance between the word line lead-out structure and corresponding words line is increased, so that a current flowing through the word line is reduced, thereby reducing and the induction margin of the semiconductor device and the charging and discharging speed of the storage capacitor.

<CIT> describes the layout of a semiconductor device where embedded word line is connected to a metal wiring line by means of a contact. Background may be found in <CIT> & <CIT>.

The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and description below. Other features, objects, and advantages of the disclosure will be apparent from the specification, drawings, and claims.

For a clear illustration of technical solutions of embodiments of the present application, reference may be made to one or more of figures, but the additional details or examples used to describe the drawings should not be construed as limiting the scope of any one of inventions and innovations, currently described embodiments, or preferred modes of the present application.

To facilitate understanding of the present application, the present application will be described below in detail with reference to the accompanying drawings. Embodiments of the present application are illustrated in the accompanying drawings. However, the present application may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present application belongs. The terms used herein in the specification of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application.

It is to be understood that when an element or a layer is referred to as being "on", it can be directly on the other element or layer or an intervening element or layer may be present. It is to be understood that although the terms first, second, third, and the like may be used to describe various elements, components, regions, layers, doping types and/or parts, these elements, components, regions, layers, doping types and/or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type, or part from another element, component, region, layer, doping type, or part. Therefore, a first element, component, region, layer, doping type, or part discussed below may be represented as a second element, component, region, layer or part without departing from the teaching of the disclosure.

Spatial relation terms such as "under", "underneath", "lower", "below", "above", "upper", and the like, may be used herein to describe a relation between one element or feature and another element or feature as illustrated in the figures. It is to be understood that in addition to the orientation shown in the figures, the spatial relation terms further include different orientations of a device in use and operation. For example, if the device in the figures is turned over, the element or feature described as "underneath the other element" or "below it" or "under it", the element or feature will be oriented "over" the other element or feature. Therefore, the exemplary terms "underneath" and "below" may include both above and below. In addition, the device may also include additional orientations (for example, rotated <NUM> degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

As used herein, the singular forms "a", "an", and "the/the" can also include the plural forms, unless the context clearly indicates otherwise. It is also to be understood that the terms "comprise/include" or "have" or the like specify the presence of a stated feature, integer, step, operation, component, part, or a combination thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Meanwhile, in the specification, the term "and/or" includes any and all combinations of the associated listed items.

<FIG> is a top view of a word line lead-out structure in one embodiment of the present application. <FIG> is a side cross-sectional view corresponding to a section line AA' in <FIG>.

As shown in combination with <FIG> and <FIG>, the word line lead-out structure includes a word line <NUM>, a contact hole <NUM>, and a metal line <NUM>.

The word line <NUM> extends along an X-axis direction.

The contact hole <NUM> is located above the word line <NUM> and covers the word line <NUM> along a Y-axis direction, and the Y-axis direction is perpendicular to the X-axis direction. The contact hole <NUM> covering the word line <NUM> along the Y-axis direction means that a width of the contact hole <NUM> along the Y-axis direction is greater than or equal to that of the word line <NUM> along the Y-axis direction, and the contact hole <NUM> covers a segment of the word line <NUM> along the X-axis direction.

The metal line <NUM> is located on the contact hole <NUM> and covers the contact hole <NUM>, that is, the contact hole <NUM> is located between the word line <NUM> and the metal line <NUM>, a bottom surface of the contact hole <NUM> is in contact with the word line <NUM>, and a top surface of the contact hole <NUM> is in contact with the metal line <NUM>. The contact area between the contact hole <NUM> and the metal line <NUM> is larger than that between the contact hole <NUM> and the word line <NUM>, and the width of the contact surface between the contact hole <NUM> and the metal line <NUM> along the Y-axis direction is greater than the width of the contact surface between the contact hole <NUM> and the word line <NUM> along the Y-axis direction.

According to the above word line lead-out structure, the word line <NUM> is formed in a semiconductor device. By forming the contact hole <NUM> and the metal line <NUM> above the word line <NUM>, an external electric signal is transmitted to the word line <NUM> through the metal line <NUM> and the contact hole <NUM>, and the semiconductor device is controlled through the word line <NUM>. In the present application, the contact hole <NUM> covers the word line <NUM> along the Y-axis direction, and the metal line <NUM> covers the contact hole <NUM>. The contact area between the contact hole <NUM> and the metal line <NUM> is larger than that between the contact hole <NUM> and the word line <NUM>. By adjusting the contact area o between the contact hole <NUM> and the word line <NUM> and the contact area between the contact hole <NUM> and the metal line <NUM>, the contact area between the contact hole <NUM> and the word line <NUM> is relatively small, so that the influence of the contact hole <NUM> on the integration level of the device is reduced. The contact area between the contact hole <NUM> and the metal line <NUM> is relatively large, so that the contact resistance of the whole word line lead-out structure is reduced, thereby improving the induction margin of the semiconductor memory and the charging and discharging speed of a storage capacitor.

In one embodiment, as shown in <FIG>, a cross-section of the contact hole <NUM> is a T-shaped structure, that is, a section of the contact hole <NUM> along a Z-axis direction shown in <FIG> is the T-shaped structure. The X-axis, the Y-axis, and the Z-axis are perpendicular to each other. In this embodiment, the contact hole <NUM> is the T-shaped structure, and the width of the top surface of the contact hole <NUM> along the Y-axis direction is greater than the width of the bottom surface the contact hole <NUM> along the Y-axis direction, so that the contact area between the contact hole <NUM> and the metal line <NUM> is larger than that between the contact hole <NUM> and the word line <NUM>.

More specifically, a substrate <NUM> is provided with a first groove <NUM> extending along the X-axis direction, the word line <NUM> is filled in the first groove <NUM>, and the thickness of the word line <NUM> is smaller than the depth of the first groove <NUM>, that is, the top surface of the word line <NUM> is lower than the top surface of the substrate <NUM>. A part of the contact hole <NUM> is filled in the first groove <NUM>, the contact hole <NUM> located outside the first groove <NUM> extends to the substrate <NUM> at both sides of the word line <NUM> along the Y-axis direction. At this time, the contact hole <NUM> located in the first groove <NUM> together with the contact hole <NUM> located outside the first groove <NUM> together form the contact hole <NUM> with the T-shaped structure. Further, the width of the metal line <NUM> above the contact hole <NUM> along the Y-axis direction is equal to that of the contact hole <NUM> along the Y-axis direction, and side surfaces of the contact hole <NUM> and the metal line <NUM> extending along the X-axis direction are aligned with each other. In one embodiment, the word line <NUM> includes a metal structure <NUM> located at the bottom of the first groove <NUM>, and a polysilicon structure located at the top of the metal structure <NUM>. The polysilicon structure of the word line in a region covered by the contact hole <NUM> is removed, that is, the word line in the region covered by the contact hole <NUM> does not include the polysilicon structure, and the contact hole <NUM> is in direct contact with the metal structure <NUM>, thereby reducing parasitic resistance between the word lines.

In one embodiment, as shown in combination with <FIG> and <FIG>, the word line lead-out structure includes <NUM> * N word lines <NUM>, each of the word line <NUM> is distributed in parallel along the Y-axis direction, <NUM> * N contact holes <NUM> are respectively formed on the <NUM> * N word lines <NUM>, <NUM> * N metal lines <NUM> are respectively formed on the <NUM> * N contact holes <NUM>, and each of the metal line <NUM> extends along the X-axis direction. N is a positive integer, and the <NUM> * N word lines <NUM>, the <NUM> * N contact holes <NUM> and the <NUM> * N metal lines <NUM> are in one-to-one correspondence. In this embodiment, the <NUM> * N word lines <NUM> which are distributed in parallel along the Y-axis direction are formed on the substrate <NUM>. The contact hole <NUM> and the metal line <NUM> corresponding to each word line <NUM> are formed above each word line <NUM>, that is, each word line <NUM> corresponds to one independent word line lead-out structure, so that each word line <NUM> is independently controlled. Further, the <NUM> * N word lines <NUM> are aligned in the Y-axis direction, that is, the <NUM> * N word lines <NUM> are the same in length along the X-axis direction, and an endpoint of each of the word lines <NUM> is aligned along the Y-axis direction.

More specifically, as shown in <FIG>, N metal lines <NUM> and N contact holes <NUM> are located at one side of the word line <NUM> along the X-axis direction, and the other N metal lines <NUM> and the other N contact holes <NUM> are located at the other side of the word line <NUM> along the X-axis direction. The metal lines <NUM> at the same side are distributed in parallel along the Y-axis direction. In this embodiment, <NUM> * N lead-out structures formed by the <NUM> * N contact holes <NUM> and the <NUM> * N metal lines <NUM> are divided into two groups of the lead-out structures. A first group of the lead-out structures include N contact holes <NUM>, and N metal lines <NUM> in contact with the N contact holes <NUM>. A second group of lead-out structures include further N contact holes <NUM>, and further N metal lines <NUM> in contact with the further N contact holes <NUM>. The first group of lead-out structures is close to one endpoint of the word line <NUM>, and the second group of lead-out structures is close to the other endpoint of the word line <NUM>. By dispersedly arranging the metal line <NUM> and the contact hole <NUM> at both sides of the word line <NUM>, the width of the metal line <NUM> or the contact hole 310can be appropriately increased, thereby reducing the contact resistance of the word line lead-out structure.

Further, the contact hole <NUM> and the metal line <NUM> at one side of the word line <NUM> cover the odd-numbered word lines <NUM>, and the contact hole <NUM> and the metal line <NUM> at the other side of the word line <NUM> cover the even-numbered word lines <NUM>. In this embodiment, the <NUM> * N word lines <NUM> are sequentially arranged along the Y-axis direction, the first group of the lead-out structures are arranged on the odd-numbered word lines <NUM>, and the second group of the lead-out structures are arranged on the even-numbered word lines <NUM>, so that the space between adjacent contact holes <NUM> is increased, further, the width of the contact hole <NUM> and the metal line <NUM> is increased, the contact area is increased, and the contact resistance is reduced.

In one embodiment, the conductivity of the contact hole <NUM> is different from the conductivity of the metal line <NUM>, that is, materials of the metal line <NUM> and the contact hole <NUM> are different. Specifically, the material of the contact hole <NUM> may be metal or metal alloy including one or more of copper, aluminum, nickel, tungsten, silver, gold, and the like. The metal line <NUM> may be one of a copper line, an aluminum line, a nickel line, a tungsten line, a silver line, a gold line, and the like.

<FIG> shows a method for preparing a word line lead-out structure in one embodiment of the present application.

In one embodiment according to the invention, the method for preparing a word line lead-out structure includes the following operations.

At S100: a first groove extending along an X-axis direction is formed in a substrate.

At S200, a word line extending along the X-axis direction is formed in the first groove. A top surface of the word line is lower than that of the substrate.

In combination with <FIG> and <FIG>, <FIG> is a top view in which the word line <NUM> is formed, and <FIG> is a side cross-sectional view corresponding to a section line AA' in <FIG>.

Specifically, the first groove <NUM> extending along the X-axis direction is provided in the substrate <NUM>, the word line <NUM> extending along the X-axis direction is formed in the first groove <NUM>. The top surface of the word line <NUM> is lower than the top surface of the substrate <NUM>, that is, the thickness of the word line <NUM> is smaller than the depth of the first groove <NUM>. Further, the word line <NUM> includes a metal structure <NUM> at the bottom of the first groove <NUM> and a polysilicon structure <NUM> located on the metal structure <NUM>.

In a specific embodiment, as shown in <FIG>, the substrate <NUM> is provided with <NUM> * N first grooves <NUM> respectively extending along the X-axis direction, and each of the grooves is distributed in parallel along the Y-axis direction. <NUM> * N word lines <NUM> extending along the X-axis direction are formed in the <NUM> * N first grooves <NUM>, and each of the word lines <NUM> is distributed in parallel along the Y-axis direction. Further, the above word lines <NUM> are aligned in the Y-axis direction, that is, the <NUM> * N word lines <NUM> are the same in length along the X-axis direction, and an endpoint of each of the word lines <NUM> is aligned along the Y-axis direction.

In a specific embodiment, a procedure of forming the word line <NUM> includes the following operations.

At S210: a word line material layer is deposited in the first groove and on the substrate outside the first groove.

Specifically, one word line material layer is deposited through a deposition process. The word line material layer has certain thickness and covers the first groove <NUM> and the substrate <NUM>.

At S220: the top surface of the word line material layer is flattened; the word line material layer on the substrate is removed so that the word line material layer in the first groove is reserved.

After the word line material layer is deposited, the word line material layer has an uneven upper surface. Next, the upper surface of the word line material layer is ground through a chemical mechanical grinding process, so that the upper surface of the word line material layer is flattened. The word line material layer is etched to expose the substrate <NUM>, so that the word line material layer in the first groove <NUM> is reserved.

At S230: the word line material layer in the first groove is etched back, the word line material layer at the top of the first groove is removed, so that the word line material layer at the bottom of the first groove is reserved, thereby forming the word line.

Specifically, the word line material layer in the first groove <NUM> is etched through an etching process to reduce the thickness of the word line material layer, so that the thickness of the word line material layer is smaller than the depth of the first groove <NUM>. After etching is stopped, the reserved word line material layer forms the word line <NUM>. The etch-back depth of the word line material layer can be flexibly selected according to specific requirements.

After the word line <NUM> is formed, execution is continued.

At S300: a contact hole layer is formed on the word line and on the substrate outside the first groove.

In one embodiment, the contact hole layer <NUM> is formed directly on the word line <NUM> and on the substrate <NUM> outside the first groove <NUM>.

According to the invention, S300 includes the following sub-operations.

At S311: a dielectric layer is formed on the substrate and the first groove.

The dielectric layer <NUM> is deposited on the substrate <NUM> and the first groove <NUM> through the deposition process, and the top surface of the dielectric layer <NUM> is ground to flatten the top surface of the dielectric layer <NUM>.

At S312: the dielectric layer is etched to form a second groove extending along the Y-axis direction. The second groove penetrates through the dielectric layer and exposes the word line and the substrate.

As shown in <FIG> and <FIG>, <FIG> is a top view in which a second groove <NUM> is formed in the dielectric layer <NUM>, and <FIG> corresponds to a side cross-sectional view of a section line AA' in <FIG>. The dielectric layer <NUM> is etched. The second groove <NUM> extending along the Y-axis direction is formed on the dielectric layer <NUM>. The second groove <NUM> penetrates through the dielectric layer <NUM> along a Z-axis direction and exposes the word line <NUM> (specifically, the polysilicon structure <NUM> in the word line <NUM>) and the substrate <NUM> at the bottom of the second groove <NUM>. It is to be noted that in this embodiment, the etching selectivity ratio of the dielectric layer <NUM> and the substrate <NUM> is different, so that the substrate <NUM> is not substantially etched during the etching of the dielectric layer <NUM> to form the second groove <NUM>.

In one embodiment, as shown in <FIG>, two second grooves <NUM> respectively extending along the Y-axis direction are formed in the dielectric layer <NUM>. One of the second grooves <NUM> is located at one side of the word line <NUM> extending along the X-axis direction, and the other of the second grooves <NUM> is located at the other side of the word line <NUM> extending along the X-axis direction, that is, the two second grooves <NUM> are distributed in parallel along the X-axis direction. Further, the two second grooves <NUM> are respectively close to end points on two sides of the word line <NUM> along the X-axis direction.

In a specific embodiment, as shown in <FIG> and <FIG>, <FIG> is a top view in which an exposed polysilicon structure is removed, and <FIG> corresponds to a side cross-sectional view of a section line AA' in <FIG>. When the polysilicon structure <NUM> of the word line is exposed due to the second groove <NUM>, execution is continued. The exposed polysilicon structure <NUM> is removed, so that the metal structure <NUM> is reserved.

At S313: the contact hole layer is formed in the first groove and the second groove.

As shown in <FIG> and <FIG>, <FIG> is a top view in which the first groove <NUM> and the second groove <NUM> are filled with the contact hole layer <NUM>, and <FIG> corresponds to a side cross-sectional view of a section line AA' in <FIG>. A thicker layer of contact hole material is deposited through a deposition process, the contact hole material fills the exposed first groove <NUM> and second groove <NUM> and is higher than the dielectric layer <NUM>, then the contact hole material is flattened through a grinding process, the contact hole material above the dielectric layer <NUM> is removed, so that only the contact hole material in the first groove <NUM> and the second groove <NUM> is reserved, thereby forming the required contact hole layer <NUM>.

In the above embodiment, the contact hole layer <NUM> is formed through S311 to S313. In other embodiments, the required contact hole layer <NUM> can also be formed through the following sub-operations S321 to S323.

At S321: the contact hole material is deposited on the substrate <NUM> and the first groove <NUM>.

At S322: the contact hole material is etched, so that the contact hole material at two sides is removed to form the contact hole layer <NUM> extending along the Y-axis direction.

At S323: a dielectric material is deposited and flattened. The dielectric material layer above the contact hole layer <NUM> is removed, the contact hole layer <NUM> is exposed, and the dielectric material at two sides of the contact hole layer <NUM> is reserved to form the dielectric layer <NUM>.

Through the above steps, after the contact hole layer <NUM> is formed, execution is continued.

At S400: a metal layer is formed on the contact hole layer.

As shown in <FIG> and <FIG>, <FIG> is a top view in which a metal layer <NUM> is formed, and <FIG> is a side cross-sectional view corresponding to a section line AA' in <FIG>. The metal layer <NUM> is formed on the contact hole layer <NUM> through the deposition process. In one embodiment, the contact hole layer <NUM> is formed in the second groove <NUM>, and the metal layer <NUM> is formed on the contact hole layer <NUM> and the dielectric layer <NUM>.

At S500: the metal layer and the contact hole layer are etched to form the word line lead-out structure.

After the metal layer <NUM> is formed on the contact hole layer <NUM>, the metal layer <NUM> and the contact hole layer <NUM> are etched. The metal layer <NUM> is etched to form the metal line <NUM>, and the contact hole layer <NUM> is etched to form the contact hole <NUM>, so that the word line lead-out structure is formed. A location relation of the word line <NUM>, the contact hole <NUM> and the metal line <NUM> in the word line lead-out structure has been described above and will not be described in detail herein.

In one embodiment, the operation that the metal layer <NUM> and the contact hole layer <NUM> are etched specifically includes that: a mask is formed on the metal layer <NUM>, the exposed metal layer <NUM> is etched downward under the protection of the mask to form the metal line <NUM>, and the exposed contact hole layer <NUM> is continuously etched downward under the protection of the metal line <NUM> to form the contact hole <NUM>. That is, the above etching of the contact hole layer <NUM> belongs to self-aligned etching, and boundaries of the contact hole <NUM> and the metal line <NUM> formed after the self-aligned etching are aligned, so that an influence on the electric performance of a device resulted from an offset between the contact hole layer <NUM> and the metal line <NUM> is prevented.

In a specific embodiment, <NUM> * N word lines <NUM> are formed on the substrate <NUM>, and the contact hole layer <NUM> is formed in the second groove <NUM> and extends along the Y-axis direction. At this time, S500 includes the following operations.

At S510: <NUM> * N masks are formed on the metal layer; each of the masks spans the second groove <NUM> along the X-axis direction and covers a word line along the Y-axis direction.

As shown in <FIG> and <FIG>, <FIG> is a top view in which <NUM> * N masks <NUM> are formed, and <FIG> corresponds to a side cross-sectional view of a section line AA' in <FIG>. The <NUM> * N masks <NUM> are formed on the metal layer <NUM>, each of the masks <NUM> spans the second groove <NUM> along the X-axis direction and one mask <NUM> covers one word line <NUM> along the Y-axis direction, that is, the <NUM> * N masks <NUM> and the <NUM> * N word lines <NUM> are in one-to-one correspondence. Furthermore, two second grooves <NUM> are formed in the dielectric layer <NUM>, when two contact hole layers <NUM> extending along the Y-axis direction are respectively correspondingly formed in the two second grooves <NUM>, among the <NUM> * N masks <NUM>, N masks <NUM> are located at one side of the metal layer <NUM> along the X-axis direction and span the second grooves <NUM> located at the same side along the X-axis direction, and respectively cover the odd-numbered word lines <NUM>. The other N masks <NUM> are located at the other side of the metal layer <NUM> along the X-axis direction and span the other second grooves <NUM> located at the same side along the X-axis direction, and respectively cover the even-numbered word lines. Further, the masks <NUM> at the same side are distributed in parallel along the Y-axis direction.

At S520: the metal layer and the contact hole layer are sequentially etched, the metal layer below the mask is reserved to form <NUM> * N metal lines, and the contact hole layer below the metal line is reserved to form <NUM> * N contact holes. N is a positive integer, and the <NUM> * N word lines, the <NUM> * N contact holes and the <NUM> * N metal lines are in one-to-one correspondence.

As shown in <FIG> and <FIG>, <FIG> is a top view in which the <NUM> * N metal lines <NUM> are formed, and <FIG> corresponds to a side cross-sectional view of a section line AA' in <FIG>. The exposed metal layer <NUM> is etched under the protection of the <NUM> * N masks to form the <NUM> * N independent metal lines <NUM>, and the exposed contact hole layer <NUM> is continuously etched under the protection of the metal lines <NUM> to form the <NUM> * N independent contact holes <NUM>. At this time, the <NUM> * N word lines <NUM>, the <NUM> * N contact holes <NUM> and the <NUM> * N metal lines <NUM> are in one-to-one correspondence. Each of the word lines <NUM> is led out through the contact hole <NUM> and the metal line <NUM> above the word line <NUM>.

In the embodiment, the contact hole layer <NUM> extending along the Y-axis direction is formed first, the contact hole layer <NUM> is integrally formed and electrically connected with multiple word lines <NUM>, then the metal layer <NUM> is formed on the contact hole layer <NUM> and on the dielectric layer <NUM>, the mask <NUM> is formed on the metal layer <NUM>, the mask <NUM> spans the second groove <NUM> along the X-axis direction. Next, the exposed metal layer <NUM> and contact hole layer <NUM> are sequentially etched under a shielding effect of the mask <NUM>, the contact hole layer <NUM> extending along the Y-axis direction is cut into multiple independent parts. The metal layer <NUM> and contact hole layer <NUM> that are not etched form a lead-out structure of the word line <NUM>. Since the self-aligned etching is used for the contact hole layer <NUM> as described above, an alignment step of front and back etching in a conventional technology is omitted. In the present application, the boundaries of the reserved metal layer <NUM> and the reserved contact hole layer <NUM> after etching are flush, the metal layer <NUM> and the contact hole layer <NUM> do not have location offset, thereby greatly improving the electric performance of a semiconductor device.

The above-described word line lead-out structure is formed by the above preparation method of a word line lead-out structure. The contact hole <NUM> covers the word line <NUM> along the Y-axis direction, the metal line <NUM> covers the contact hole <NUM>, and the contact area between the contact hole <NUM> and the metal line <NUM> is larger than the contact area between the contact hole <NUM> and the word line <NUM>. According to the above word line lead-out structure, through adjustment of the contact area between the contact hole <NUM> and the word line <NUM>, and the contact area between the contact hole <NUM> and the metal line <NUM>, the contact area between the contact hole <NUM> and the word line <NUM> is relatively small, so that the influence of the contact hole <NUM> on the integration level of the device is reduced. The contact area between the contact hole <NUM> and the metal line <NUM> is relatively large, so that the contact resistance of the whole word line lead-out structure is reduced, thereby improving the induction margin of the semiconductor memory and the charging and discharging speed of a storage capacitor.

Claim 1:
A method for preparing a word line lead-out structure, comprising:
providing a first groove (<NUM>) in a substrate (<NUM>);
forming the word line (<NUM>) extending along the X-axis direction in the first groove (<NUM>), a top surface of the word line (<NUM>) being lower than a top surface of the substrate (<NUM>);
forming the contact hole layer (<NUM>) on the word line (<NUM>) and the substrate (<NUM>);
forming the metal layer (<NUM>) on the contact hole layer (<NUM>); and
etching the metal layer (<NUM>) and the contact hole layer (<NUM>) to form the word line lead-out structure,
wherein said forming the contact hole layer (<NUM>) on the word line (<NUM>) and the substrate (<NUM>) comprises:
forming a dielectric layer (<NUM>) on the substrate (<NUM>) and the word line (<NUM>),
etching the dielectric layer (<NUM>) to form a second groove extending along the Y-axis direction, the second groove penetrating through the dielectric layer (<NUM>) and exposing the word line (<NUM>) and the substrate (<NUM>), and
forming the contact hole layer (<NUM>) in the first groove (<NUM>) and the second groove (<NUM>).