CN115117060A - Buried word line structure and method of making the same - Google Patents

Abstract

The present invention provides a buried word line structure and a manufacturing method thereof. The buried word line structure includes a first isolation structure, a buried word line, a first barrier layer, a second barrier layer, a channel layer, and a second isolation structure. The first isolation structure is disposed in the substrate and has a trench. The buried word line is disposed on the bottom surface of the trench. The first barrier layer is disposed between the buried word line and the sidewall and bottom surface of the trench. The second barrier layer covers the top surface of the buried word line, and includes a main body portion and an extension portion, wherein the main body portion is located on the buried word line, and the extension portion extends from the buried word line The circumference of the main body portion extends upward. The channel layer is disposed on the first barrier layer and the second barrier layer. The second isolation structure is disposed on the channel layer.

Description

Buried word line structure and method of making the same

technical field

The present invention relates to a semiconductor structure and a manufacturing method thereof, in particular to a buried word line structure and a manufacturing method thereof.

Background technique

In order to improve the integration level of dynamic random access memory to speed up the operation speed of components and meet the needs of consumers for miniaturized electronic devices, buried wordline dynamic random access memory (Buried wordline DRAM) has been developed in recent years to meet the needs of consumers. the above requirements.

In general, buried word lines may be provided in isolation structures. However, when the distance between the buried word line and the capacitor disposed on the substrate is too close, the electrons stored in the capacitor are easily attracted by the electric field generated by the buried word line, resulting in the generation of leakage current.

SUMMARY OF THE INVENTION

The present invention is directed to a buried word line structure, wherein the buried word line is provided with a channel layer, and the channel layer is connected to a barrier layer arranged around the buried word line.

The present invention is directed to a method for manufacturing a buried word line structure, which is used to manufacture the above buried word line structure.

According to an embodiment of the present invention, the buried word line structure includes a first isolation structure, a buried word line, a first barrier layer, a second barrier layer, a channel layer, and a second isolation structure. The first isolation structure is disposed in the substrate and has a trench. The buried word line is disposed on the bottom surface of the trench. The first barrier layer is disposed between the buried word line and the sidewall and bottom surface of the trench. The second barrier layer covers the top surface of the buried word line, and includes a main body portion and an extension portion, wherein the main body portion is located on the buried word line, and the extension portion extends from the main body The circumference of the part extends upwards. The channel layer is disposed on the first barrier layer and the second barrier layer. The second isolation structure is disposed on the channel layer.

According to an embodiment of the present invention, a method for fabricating a buried word line structure includes the following steps. First, a first isolation structure is formed in the substrate. Next, trenches are formed in the first isolation structure. Then, a first barrier layer is formed on the lower sidewall and bottom surface of the trench. Next, a buried word line is formed on the first barrier layer. Then, a second barrier layer is formed on the top surface of the buried word line, wherein the second barrier layer includes a body portion and an extension portion, the body portion is located on the buried word line, and The extension portion extends upwardly from the periphery of the body portion. Next, a channel layer is formed on the first barrier layer and the second barrier layer. Afterwards, a second isolation structure is formed on the channel layer.

Based on the above, in the buried word line structure of the present invention, the barrier layer with the extension portion is formed on the buried word line, and the channel layer is formed on the barrier layer with the extension portion and extends downward beside the extension portion It is connected to another barrier layer formed around the buried word line. In this way, when the device is operated, the electric field in the corner region adjacent to the buried word line can be effectively reduced to prevent the electrons stored in the capacitor from being attracted by the electric field generated by the buried word line and causing leakage. generation of current.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, the following embodiments are given and described in detail with the accompanying drawings as follows.

Description of drawings

1A to FIG. 1G are schematic cross-sectional views illustrating a manufacturing process of a buried word line structure according to an embodiment of the present invention.

Detailed ways

1A to FIG. 1G are schematic cross-sectional views illustrating a manufacturing process of a buried word line structure according to an embodiment of the present invention.

1A, a substrate 100 is provided. The substrate 100 may be a semiconductor substrate, and in this embodiment, the substrate 100 is, for example, a silicon substrate. Next, a first isolation structure 102 is formed in the substrate 100 . The first isolation structure 102 is, for example, a shallow trench isolation (shallow trench isolation, STI). In this embodiment, the material of the first isolation structure 102 is, for example, silicon nitride, but the present invention is not limited thereto. In other embodiments, the material of the first isolation structure 102 may also be silicon oxide. After that, trenches 104 are formed in the first isolation structure 102 . The trench 104 is used to define the area of the buried word line to be formed later.

Referring to FIG. 1B , after the trench 104 is formed, an insulating layer 106 may be formed on the sidewalls and the bottom surface of the trench 104 . The insulating layer 106 is used to reduce the interference between a plurality of buried word lines formed subsequently. In this embodiment, the insulating layer 106 is, for example, an in situ steam generation (ISSG) oxide layer, but the invention is not limited thereto. Next, a barrier material layer 108 is formed on the insulating layer 106 and the surface of the substrate 100 . In this embodiment, the barrier material layer 108 is, for example, a titanium nitride layer, but the invention is not limited thereto. Then, a word line material layer 110 is formed on the substrate 100 to fill the trenches 104 . In this embodiment, the word line material layer 110 is, for example, a tungsten layer, but the invention is not limited thereto.

Referring to FIG. 1C , an etch-back process is performed to remove part of the barrier material layer 108 and part of the word line material layer 110 to form the buried word line 112 and the sidewalls of the buried word line 112 and the trench 104 The first barrier layer 114 between the bottom surface and the bottom surface. In detail, in the present embodiment, the barrier material layer 108 and the word line material layer 110 on the surface of the substrate 100 and the sidewalls at the upper portion of the trench 104 are removed during the etch-back process. Next, a dielectric layer 116 is formed on the surface of the substrate 100 , the sidewalls of the trenches 104 , the buried word lines 112 and the first barrier layer 114 . An etching selectivity ratio is required between the dielectric layer 116 and the first isolation structure 102 . In this embodiment, since the material of the first isolation structure 102 is, for example, silicon nitride, the material of the dielectric layer 116 is, for example, silicon oxide. In other embodiments, when the material of the first isolation structure 102 is, for example, silicon oxide, the material of the dielectric layer 116 is, for example, silicon nitride. In addition, in order to prevent the subsequently formed channel layer from contacting the buried word lines 112 , the thickness of the dielectric layer 116 must not exceed the thickness of the first barrier layer 114 , which will be described in detail later.

Referring to FIG. 1D , an etch-back process is performed to remove part of the dielectric layer 116 to form a dielectric structure 118 . In detail, in this embodiment, during the etch-back process, the dielectric layer 116 on the surface of the substrate 100, on the sidewalls at the upper portion of the trench 104, and on the buried word line 112 is removed, The top surface of the buried word line 112 is exposed, and the dielectric layer 116 on the sidewalls at the lower portion of the trench 104 is preserved. The remaining dielectric layer 116 forms a dielectric structure 118 on the first barrier layer 114 . Since the thickness of the dielectric layer 116 does not exceed the thickness of the first barrier layer 114 , the formed dielectric structure 118 is only located on the first barrier layer 114 without contacting the buried word lines 112 . In addition, due to the etching selectivity ratio between the dielectric layer 116 and the first isolation structure 102, the first isolation structure 102 is not damaged during the above-mentioned etch-back process.

Referring to FIG. 1E , a barrier material layer 120 is formed on the surface of the substrate 100 , on the sidewalls of the trenches 104 , on the top surface of the buried word lines 112 , and on the dielectric structure 118 . In this embodiment, the barrier material layer 120 is, for example, a titanium nitride layer, but the invention is not limited thereto. Then, a protective material layer 122 is formed on the substrate 100 to fill the trenches 104 . In this embodiment, the protective material layer 122 is, for example, a spin-on coating (SOC) layer, but the present invention is not limited thereto.

Referring to FIG. 1F , an etch-back process is performed on the protective material layer 122 to remove part of the protective material layer 122 to form a protective layer 124 on the barrier material layer 120 . The protective layer 124 exposes the barrier material layer 120 at the upper portion of the trench 104 . In other words, the protective layer 124 covers the barrier material layer 120 on the top surface of the buried word line 112 and on the sidewalls and part of the top surface of the dielectric structure 118 . Then, using the protective layer 124 as an etching mask, an anisotropic etching process is performed to remove the barrier material layer 120 not covered by the protective layer 124 . In this way, the second barrier layer 126 is formed on the top surface of the buried word line 112 . In this embodiment, the second barrier layer 126 includes a main body portion 126a, an extension portion 126b and a horizontal portion 126c. The body portion 126a is located on the top surface of the buried word line 112, the extension portion 126b extends upward from the periphery of the body portion 126a, and the horizontal portion 126c is connected to the top of the extension portion 126b to form a second “U”-shaped cross-section. Barrier layer 126 .

The cross-sectional shape of the second barrier layer 126 can be changed by controlling the thickness of the formed barrier material layer 120 . For example, in the present embodiment, the thickness of the barrier material layer 120 is smaller than the width of the dielectric structure 118, so the second barrier layer 126 formed may have a horizontal portion 126c. In another embodiment, when the thickness of the barrier material layer 120 is equal to the width of the dielectric structure 118, the formed second barrier layer 126 does not have the horizontal portion 126c. In addition, the thickness of the barrier material layer 120 cannot be greater than the width of the dielectric structure 118, otherwise the second barrier layer with the extended portion cannot be formed.

Referring to FIG. 1G , an etching process is performed to remove the dielectric structure 108 and the protective layer 124 . Next, a channel layer 128 is formed on the first barrier layer 114 and the second barrier layer 126 . The method of forming the channel layer 128 is, for example, firstly forming a channel material layer on the substrate 100 to fill the trench 104 , and then performing an etch back process to remove the trench on the surface of the substrate 100 and the upper part of the trench 104 . material layer. In particular, when the device is operated, the electric field generated by the channel layer 128 must be lower than the electric field generated by the buried word line 112, which will be further described later. Therefore, in this embodiment, when the buried word line 112 is, for example, a tungsten layer, the channel layer 128 is, for example, a polysilicon layer, but the invention is not limited thereto. In this embodiment, after the etch back process is performed, the second barrier layer 126 is not exposed, that is, the channel layer 128 completely covers the second barrier layer 126 and is around the second barrier layer 126 It is in contact with the first barrier 114 layer, but the present invention is not limited thereto. In other embodiments, after the above-mentioned etch-back process, the channel layer 128 may expose part of the second barrier layer 126 , and the channel layer 128 is still around the second barrier layer 126 and the first barrier layer 114 layer contact. For example, the horizontal portion 126c and a portion of the extended portion 126b of the second barrier layer 126 may be exposed. After that, a second isolation structure 130 is formed on the channel layer 128 to complete the buried word line structure 10 of the present embodiment. In this embodiment, the material of the second isolation structure 130 is, for example, silicon nitride, so as to avoid damage to the oxide layer on the substrate 100 during subsequent processes.

The buried word line structure of the present invention will be described below by taking FIG. 1G as an example.

Referring to FIG. 1G , in the buried word line structure 10 , the second barrier layer 126 having the extended portion 126 b is disposed on the buried word line 112 , the channel layer 128 is disposed on the second barrier layer 126 and on the The extension portion 126b extends downward and is connected to the first barrier layer 114 . In this way, when the device is operated, the electric field in the corner regions adjacent to the buried word lines 112 can be effectively reduced, so that the electrons stored in the capacitors subsequently formed on the substrate 100 are not easily absorbed by the buried word lines. The electric field generated by the wire 112 attracts, thereby reducing or even avoiding the generation of leakage current.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (10)

1. a buried word line structure, is characterized in that, comprises: a first isolation structure, disposed in the substrate, and having a trench; a buried word line, disposed on the bottom surface of the trench; a first barrier layer, disposed between the buried word line and the sidewall and bottom of the trench; The second barrier layer covers the top surface of the buried word line and includes a main body portion and an extension portion, wherein the main body portion is located on the buried word line, and the extension portion is formed from the main body portion extending upwards around the a channel layer disposed on the first barrier layer and the second barrier layer; and The second isolation structure is disposed on the channel layer. 2 . The buried word line structure of claim 1 , wherein the channel layer covers the second barrier layer and is in contact with the first barrier layer. 3 . 3 . The buried word line structure of claim 1 , wherein the second barrier layer further comprises a horizontal portion connected to the top of the extension portion. 4 . 4. The buried word line structure according to claim 1, further comprising an insulating layer disposed on the sidewall and bottom surface of the trench and in contact with the sidewall and bottom surface of the trench . 5. The buried word line structure of claim 1, wherein the buried word line comprises a tungsten layer. 6. The buried word line structure of claim 1, wherein the channel layer comprises a polysilicon layer. 7. A method for manufacturing a buried word line structure, comprising: forming a first isolation structure in the substrate; forming a trench in the first isolation structure; forming a first barrier layer on the lower sidewall and bottom surface of the trench; forming buried word lines on the first barrier layer; A second barrier layer is formed on the top surface of the buried word line, wherein the second barrier layer includes a main body portion and an extension portion, the main body portion is located on the buried word line, and the an extension portion extends upwardly from the periphery of the body portion; forming a channel layer on the first barrier layer and the second barrier layer; and A second isolation structure is formed on the channel layer. 8. The method for manufacturing a buried word line structure according to claim 7, wherein the method for forming the second barrier layer comprises: After forming the buried word line, a dielectric layer is formed on the surface of the substrate, on the sidewall of the trench, on the first barrier layer and on the buried word line, wherein the thickness of the dielectric layer does not exceed the thickness of the first barrier layer; removing part of the dielectric layer to form a dielectric structure on the first barrier layer and exposing the top surface of the buried word line; forming a barrier material layer on the surface of the substrate, on the sidewalls of the trench, on the dielectric structure and on the top surface of the buried word line; forming a protective layer on the barrier material layer, wherein the protective layer exposes the barrier material layer at the upper portion of the trench; using the protective layer as a mask, performing an anisotropic etching process to remove part of the barrier material layer; and The protective layer and the dielectric structure are removed. 9 . The method of claim 7 , wherein the channel layer covers the second barrier layer and is in contact with the first barrier layer. 10 . 10 . The method for manufacturing a buried word line structure according to claim 7 , wherein before forming the first barrier layer, further comprising forming an insulating layer on the sidewall and bottom surface of the trench. 11 . .

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