Preparation method of conductive contact hole
By combining the selective etching process with isotropic and anisotropic etching, the problem of insufficient alignment accuracy between the conductive contact holes and the structures to be contacted is solved, achieving high-precision alignment and cost reduction.
Patent Information
- Application Number
- CN202510767875.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-10
- Publication Date
- 2025-10-03
AI Technical Summary
In semiconductor manufacturing, the alignment accuracy between the conductive contact hole and the structure to be contacted is difficult to ensure, especially when there is a boss structure. Slight deviations may lead to misalignment and affect product yield.
A selective etching process is used to expose the top of the structure to be contacted by removing part of the dielectric layer, and gradually etching to form a conductive contact hole. The sidewall angle and depth are controlled by combining isotropic and anisotropic etching processes to avoid alignment deviation in the photolithography process.
It improves the alignment accuracy between the conductive contact hole and the structure to be contacted, breaks through the overlay accuracy limit of the photolithography machine, is suitable for smaller structures, reduces the use of photolithography masks, and reduces production costs.
Smart Images
Figure CN120749077A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of semiconductor technology, and in particular to a method for preparing a conductive contact hole. Background Art
[0002] In semiconductor manufacturing, photolithography is a common method for creating conductive contact holes. The main process involves first forming a photoresist on a dielectric layer covering the structure to be contacted. Using exposure and development, the pattern is transferred to the photoresist to locate the conductive contact hole. The patterned photoresist is then used as a mask to etch the dielectric layer and the structure to be contacted, ultimately forming the conductive contact hole. However, during the exposure process, alignment deviation is very likely to occur. If this deviation is too large, the conductive contact hole cannot be formed in the designated area, directly affecting product yield. This is especially true when the structure to be contacted has a boss structure. Even a slight deviation can cause the conductive contact hole to misalign with the structure to be contacted.
[0003] Therefore, how to improve the alignment accuracy between the conductive contact hole and the structure to be contacted has become an urgent problem to be solved in this field. Summary of the Invention
[0004] In view of this, an embodiment of the present application provides a method for preparing a conductive contact hole to solve at least one problem existing in the background technology.
[0005] In a first aspect, an embodiment of the present application provides a method for preparing a conductive contact hole, the method comprising:
[0006] Providing a semiconductor structure, the semiconductor structure comprising a substrate and a structure to be contacted, the substrate comprising a first surface and a second surface opposite to each other, the structure to be contacted at least partially protruding from the first surface;
[0007] forming a dielectric layer on the semiconductor structure, wherein the dielectric layer buries the structure to be contacted;
[0008] removing a portion of the dielectric layer to expose the top of the structure to be contacted;
[0009] A selective etching process is performed to gradually etch the structure to be contacted through the exposed top portion to form a conductive contact hole.
[0010] In combination with the first aspect of the present application, in an optional implementation manner, the removing of a portion of the thickness of the dielectric layer is achieved by an isotropic dry etching process.
[0011] In conjunction with the first aspect of the present application, in an optional embodiment, the angle between the sidewall and the bottom wall of the conductive contact hole is an obtuse angle, and performing the selective etching process includes:
[0012] performing a first dry etching process mainly based on isotropic etching to control an initial tilt angle of the sidewall of the conductive contact hole;
[0013] A second dry etching process mainly based on anisotropic etching is performed to deepen the depth of the conductive contact hole and achieve a final tilt angle of the sidewall of the conductive contact hole.
[0014] In combination with the first aspect of the present application, in an optional embodiment, the first etching process mainly based on isotropic etching is performed until the top surface of the etched structure to be contacted is coplanar with the top surface of the dielectric layer.
[0015] In combination with the first aspect of the present application, in an optional embodiment, the etching gas in the first etching process includes Cl2, HBr and O2.
[0016] In combination with the first aspect of the present application, in an optional embodiment, the ratio of the Cl2 gas flow rate, the HBr gas flow rate and the O2 gas flow rate ranges from 1:1:0.5 to 1:3:0.5.
[0017] In conjunction with the first aspect of the present application, in an optional embodiment, the gas flow rate of Cl2 is in the range of 50 sccm-100 sccm;
[0018] The HBr gas flow rate ranges from 100 sccm to 250 sccm;
[0019] The O2 gas flow rate ranges from 25 sccm to 50 sccm.
[0020] In combination with the first aspect of the present application, in an optional embodiment, the etching gas in the second etching process includes SF6, HBr and O2.
[0021] In combination with the first aspect of the present application, in an optional embodiment, the ratio of the SF6 gas flow rate, the HBr gas flow rate and the O2 gas flow rate is in the range of 1:5:1-1:7:1.
[0022] In conjunction with the first aspect of the present application, in an optional embodiment, the SF6 gas flow rate ranges from 10 sccm to 20 sccm;
[0023] The HBr gas flow rate ranges from 100 sccm to 200 sccm;
[0024] The O 2 gas flow rate ranges from 3 sccm to 7 sccm.
[0025] The method for preparing a conductive contact hole provided in an embodiment of the present application, for a structure to be contacted that at least partially protrudes from the first surface of the substrate and is buried by a dielectric layer, removes a portion of the dielectric layer to expose the top of the structure to be contacted, and then performs a selective etching process to gradually etch the structure to be contacted through the exposed top to form the conductive contact hole. Thus, the use of a selective etching process can reduce damage to the dielectric layer. When etching the structure to be contacted, the removed portion of the dielectric layer is used as an etching mask, and an etching process that is selective for the dielectric layer and the structure to be contacted is combined to achieve self-aligned etching, thereby avoiding alignment deviation problems caused by photolithography processes, improving the alignment accuracy of the conductive contact hole and the structure to be contacted, and overcoming the limitations of the overlay accuracy of photolithography machines. The method is suitable for smaller structures to be contacted, reduces the use of photolithography masks, and reduces production costs.
[0026] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:
[0028] Figure 1 A schematic flow chart of a method for preparing a conductive contact hole provided in an embodiment of the present application;
[0029] Figures 2 to 5 A schematic diagram of the cross-sectional structure of a conductive contact hole during the preparation process provided in an embodiment of the present application;
[0030] Figure 6 This is an electron microscope image of the conductive contact hole provided in an embodiment of the present application. DETAILED DESCRIPTION
[0031] The exemplary embodiments disclosed herein will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the specific embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.
[0032] In the following description, numerous specific details are provided to provide a more thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present application; that is, all features of actual embodiments are not described herein, nor are well-known functions and structures described in detail.
[0033] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.
[0034] When an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. Although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, or part discussed below may be represented as the second element, component, region, layer, or part. However, when the second element, component, region, layer, or part is discussed, it does not necessarily mean that the first element, component, region, layer, or part exists in the present application.
[0035] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of an element or feature shown in the figures to other elements or features. In addition to the orientations shown in the figures, spatially relative terms are intended to also include different orientations of the device in use and operation. For example, if the device in the drawings is flipped, then the elements or features described as "under the other elements" or "under it" or "under it" will be oriented as "on" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.
[0036] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present application. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.
[0037] In order to fully understand the present application, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present application. The preferred embodiments of the present application are described in detail below. However, in addition to these detailed descriptions, the present application may also have other implementation methods.
[0038] Figure 1 A schematic flow chart of a method for preparing a conductive contact hole provided in an embodiment of the present application is shown in the figure. The method includes:
[0039] Step S101: providing a semiconductor structure, the semiconductor structure comprising a substrate and a structure to be contacted, the substrate comprising a first surface and a second surface opposite to each other, the structure to be contacted at least partially protruding from the first surface;
[0040] Step S102: forming a dielectric layer on the semiconductor structure, wherein the dielectric layer buries the structure to be contacted;
[0041] Step S103: removing a portion of the dielectric layer to expose the top of the structure to be contacted;
[0042] Step S104: performing a selective etching process to gradually etch the structure to be contacted through the exposed top portion to form a conductive contact hole.
[0043] In the embodiment of the present application, in the case where the structure to be contacted at least partially protrudes from the first surface of the substrate and is buried by the dielectric layer, a portion of the dielectric layer is removed to expose the top of the structure to be contacted, and then a selective etching process is performed to gradually etch the structure to be contacted through the exposed top to form a conductive contact hole. Thus, the selective etching process can reduce damage to the dielectric layer. When etching the structure to be contacted, the removed portion of the dielectric layer is used as an etching mask. In combination with an etching process that is selective for the dielectric layer and the structure to be contacted, self-aligned etching is achieved, which can avoid alignment deviation problems caused by the photolithography process, improve the alignment accuracy of the conductive contact hole and the structure to be contacted, and overcome the limitations of the overlay accuracy of the photolithography machine. It is suitable for smaller structures to be contacted and can also reduce the use of photolithography masks, reducing production costs.
[0044] First, please refer to Figure 1 , perform step S101 and step S102, provide a semiconductor structure, the semiconductor structure includes a substrate 100 and a structure to be contacted 200, the substrate 100 includes a first surface 101 and a second surface 102 opposite to each other, and the structure to be contacted 200 at least partially protrudes from the first surface 101; form a dielectric layer 300 on the semiconductor structure, and the dielectric layer 300 buries the structure to be contacted 200.
[0045] It should be noted that Figure 1 A semiconductor structure having a substrate and a structure to be contacted, and the structure to be contacted at least partially protruding from the first surface 101 is only schematically shown. The semiconductor structure in the embodiment of the present application can be any suitable semiconductor structure known to those skilled in the art; for example, the semiconductor structure is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), the structure to be contacted is a gate structure, and the gate structure at least partially protrudes from the substrate; this application does not limit this.
[0046] It should be noted that Figure 1 The top surface of the structure to be contacted 200 is schematically shown as an arc surface. The top surface of the structure to be contacted 200 may also be a plane, a conical surface, a curved surface, etc., and this application does not limit this.
[0047] The material of the structure to be contacted 200 is different from the material of the dielectric layer 300 to facilitate the subsequent selective etching process.
[0048] In this embodiment, the material of the structure to be contacted 200 may include silicon; and the material of the dielectric layer 300 may include at least one of silicon oxide, PEOX (polyethylene oxide), and BPSG (borophosphosilicate glass).
[0049] Next, please refer to Figure 3 , step S103 is performed to remove a portion of the dielectric layer 300 to expose the top of the structure to be contacted 200. Thus, when the structure to be contacted 200 is subsequently etched, the remaining dielectric layer 300 can be used as an etching mask.
[0050] Optionally, a portion of the dielectric layer 300 is removed using an isotropic dry etching process. As can be appreciated, compared to using a CMP (Chemical Mechanical Polishing) process to planarize the dielectric layer 300, using an isotropic dry etching process to process the dielectric layer 300 provides greater uniformity, reduces process complexity, and minimizes the impact on the morphology of the contact structure 200, thereby avoiding impact on subsequent selective etching processes.
[0051] Furthermore, the etching rate of the dielectric layer 300 in the isotropic dry etching process is greater than the etching rate of the contact structure 200. Selective etching gas can be used to avoid affecting the morphology of the contact structure 200.
[0052] Please refer to the following Figures 4 to 6 , step S104 is performed to perform a selective etching process to gradually etch the structure to be contacted 200 through the exposed top to form a conductive contact hole 210.
[0053] It is understandable that the selective etching process has a higher etching rate for the structure to be contacted 200 than for the dielectric layer 300, which can reduce damage to the dielectric layer 300. When etching the structure to be contacted 200, the partially removed dielectric layer 300 is used as an etching mask. Combined with an etching process that is selective for the dielectric layer 300 and the structure to be contacted 200, self-aligned etching is achieved, which can avoid the alignment deviation problem caused by the photolithography process, achieve precise alignment of the conductive contact hole 210 and the structure to be contacted 200, and overcome the limitations of the overlay accuracy of the photolithography machine. It is suitable for smaller structures to be contacted 200 and can also reduce the use of photolithography masks, thereby reducing production costs.
[0054] Alternatively, refer to Figure 4 and Figure 5 The angle between the side wall and the bottom wall of the conductive contact hole 210 is an obtuse angle. The selective etching process includes: performing a first dry etching process based on isotropic etching to control the initial inclination angle of the side wall of the conductive contact hole 210; performing a second dry etching process based on anisotropic etching to deepen the depth of the conductive contact hole 210 and achieve the final inclination angle of the side wall of the conductive contact hole 210.
[0055] It can be understood that the angle between the sidewall and the bottom wall of the conductive contact hole 210 is an obtuse angle, and the cross-sectional area of the conductive contact hole 210 gradually decreases with depth, which can avoid the formation of voids when filling the conductive material in the conductive contact hole 210 and ensure the filling effect. The embodiment of the present application uses a two-step etching process. First, a first dry etching process based on isotropic etching is performed to control the initial tilt angle of the sidewall of the conductive contact hole 210 and achieve a certain lateral etching depth to avoid the formation of a depression at the top of the sidewall of the conductive contact hole 210. Then, a second dry etching process based on anisotropic etching is performed to deepen the depth of the conductive contact hole 210 and achieve the final tilt angle of the sidewall of the conductive contact hole 210. Ultimately, a conductive contact hole 210 with smooth sidewalls and an ideal tilt angle is obtained.
[0056] In some embodiments, a first etching process based on isotropic etching is performed until the top surface of the etched structure to be contacted 200 is coplanar with the top surface of the dielectric layer 300. This prevents the first etching process from being too long and the lateral etching depth from being too large, which would cause a depression on the top of the sidewall of the conductive contact hole 210. This helps to improve the smoothness of the sidewall of the conductive contact hole 210.
[0057] In some embodiments, the etching gas in the first etching process includes Cl 2 , HBr, and O 2 .
[0058] It can be understood that Cl2 has strong isotropic ability and serves as the main etching gas that performs the main etching role in the first etching process; O2 serves as an auxiliary etching gas to promote the reaction; HBr will generate Si-Br-O polymer (polymer) during the etching process. The polymer can inhibit the etching rate of the etching gas on the side wall of the conductive contact hole 210, avoid the side wall of the conductive contact hole 210 from being recessed, and protect the morphology of the side wall of the conductive contact hole 210. HBr is used as an auxiliary etching gas for generating the polymer.
[0059] Optionally, the ratio of the gas flow of Cl2, the gas flow of HBr, and the gas flow of O2 is in the range of 1:1:0.5-1:3:0.5. It is understandable that if the ratio is less than 1:1:0.5, too little HBr is introduced, which will result in insufficient polymer production, causing the Cl2-dominated etching effect to be too strong but lacking sufficient sidewall protection, resulting in depressions in the sidewalls; if the ratio is greater than 1:3:0.5, too much HBr is introduced, which will result in excessive polymer production, hindering etching. Therefore, the embodiment of the present application controls the ratio of the gas flow of Cl2, the gas flow of HBr, and the gas flow of O2 within this range, which can better control the morphology of the sidewalls of the conductive contact hole 210 and the etching selectivity of the dielectric layer.
[0060] Furthermore, the ratio of the gas flow of Cl2, the gas flow of HBr and the gas flow of O2 is 1:2:0.5, which is more conducive to achieving the expected effect.
[0061] Optionally, the gas flow rate of Cl2 is in the range of 50 sccm-100 sccm; the gas flow rate of HBr is in the range of 100 sccm-250 sccm; and the gas flow rate of O2 is in the range of 25 sccm-50 sccm.
[0062] In some embodiments, the etching gas in the second etching process includes SF6, HBr, and O2.
[0063] It can be understood that the second etching process is mainly anisotropic etching. When etching to the ideal depth, the bottom wall of the conductive contact hole 210 may present a stephign morphology and a micro trench morphology, specifically a convexity in the middle and a concave periphery, which will eventually affect the conductive contact effect. SF6 has a strong anisotropic ability and can effectively eliminate these two morphologies, making the bottom wall of the conductive contact hole 210 tend to be flat. SF6 is used as the main etching gas in the second etching process to perform the main etching function; HBr and O2 are used as auxiliary etching gases, and Si-Br-O Polymer can suppress the etching rate of the etching gas on the sidewall, prevent the sidewall of the conductive contact hole 210 from being recessed, and protect the sidewall morphology. At the same time, as the reaction proceeds, the polymer increases, the protective effect on the sidewall is enhanced, and the angle of the sidewall becomes more inclined. Under the synergistic effect of HBr and O2, it is more conducive to achieving the final inclination angle of the sidewall of the conductive contact hole 210; O2 can also remove the polymer, preventing the polymer from remaining in the conductive contact hole 210 and affecting the conductive contact effect.
[0064] Optionally, the ratio of the SF6 gas flow rate, the HBr gas flow rate, and the O2 gas flow rate is in the range of 1:5:1-1:7:1. It is understandable that if the ratio is less than 1:5:1, too little HBr is introduced, resulting in insufficient polymer production, causing the SF6-dominated etching effect to be too strong but lacking sufficient sidewall protection, and the sidewall inclination of the conductive contact hole 210 to be too large; if the ratio is greater than 1:7:1, the HBr and ratio are unbalanced, excessive polymer production is achieved, but there is not enough O2 to carry the polymer away, resulting in excessive polymer residue, making it difficult for SF6 to continue etching inward, and a raised columnar structure is formed at the bottom of the conductive contact hole 210. Therefore, the embodiment of the present application controls the ratio of the SF6 gas flow rate, the HBr gas flow rate, and the O2 gas flow rate within this range, which can more effectively control the inclination of the conductive contact hole 210 and obtain a smooth and flat morphology.
[0065] Furthermore, the ratio of the SF6 gas flow rate, the HBr gas flow rate, and the O2 gas flow rate is 1:6:1, which is more conducive to achieving the expected effect.
[0066] Optionally, the gas flow rate of SF6 is in the range of 10 sccm-20 sccm; the gas flow rate of HBr is in the range of 100 sccm-200 sccm; and the gas flow rate of O2 is in the range of 3 sccm-7 sccm.
[0067] Next, the manufacturing method further includes: filling the conductive contact hole 210 with a conductive material to form a conductive connection structure (not shown in the figure), thereby obtaining a CT (contact) structure that conductively leads the structure to be contacted 200.
[0068] The present application also provides a conductive contact hole, which is prepared using the conductive contact hole preparation method described above. Thus, the conductive contact hole is formed by etching the structure to be contacted using a selective etching process, which can reduce damage to the dielectric layer. When etching the structure to be contacted, the partially removed dielectric layer serves as an etching mask. Combined with an etching process that is selective for the dielectric layer and the structure to be contacted, self-aligned etching is achieved, avoiding alignment deviation problems caused by photolithography processes. This improves the alignment accuracy between the conductive contact hole and the structure to be contacted, overcomes the limitations of photolithography machine overlay accuracy, is applicable to smaller structures to be contacted, reduces the use of photolithography masks, and reduces production costs.
[0069] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementation methods. Various modifications and changes may be made to the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present application that may not be explicitly described. Therefore, the above embodiments merely express several implementation methods of the present application and do not limit the scope of protection of the patent application.
Claims
1. A method for preparing a conductive contact hole, characterized in that: The method comprises: Providing a semiconductor structure, the semiconductor structure comprising a substrate and a structure to be contacted, the substrate comprising a first surface and a second surface opposite to each other, the structure to be contacted at least partially protruding from the first surface; forming a dielectric layer on the semiconductor structure, wherein the dielectric layer buries the structure to be contacted; removing a portion of the dielectric layer to expose the top of the structure to be contacted; A selective etching process is performed to gradually etch the structure to be contacted through the exposed top portion to form a conductive contact hole.
2. The method for preparing a conductive contact hole according to claim 1, wherein: The removal of a portion of the dielectric layer is achieved by an isotropic dry etching process.
3. The method for preparing a conductive contact hole according to claim 1, wherein: The angle between the sidewall and the bottom wall of the conductive contact hole is an obtuse angle, and the performing of the selective etching process includes: performing a first dry etching process mainly based on isotropic etching to control an initial tilt angle of the sidewall of the conductive contact hole; A second dry etching process mainly based on anisotropic etching is performed to deepen the depth of the conductive contact hole and achieve a final tilt angle of the sidewall of the conductive contact hole.
4. The method for preparing a conductive contact hole according to claim 3, wherein: The first etching process mainly based on isotropic etching is performed until the top surface of the structure to be contacted after etching is coplanar with the top surface of the dielectric layer.
5. The method for preparing a conductive contact hole according to claim 3, wherein: The etching gas in the first etching process includes Cl 2 , HBr and O 2 .
6. The method for preparing a conductive contact hole according to claim 5, wherein: The ratio of the Cl2 gas flow rate, the HBr gas flow rate and the O2 gas flow rate is in the range of 1:1:0.5 to 1:3:0.
5.
7. The method for preparing a conductive contact hole according to claim 6, wherein: The Cl2 gas flow rate ranges from 50 sccm to 100 sccm; The HBr gas flow rate ranges from 100 sccm to 250 sccm; The O2 gas flow rate ranges from 25 sccm to 50 sccm.
8. The method for preparing a conductive contact hole according to claim 3, wherein: The etching gas in the second etching process includes SF6, HBr and O2.
9. The method for preparing a conductive contact hole according to claim 8, wherein: The ratio of the SF6 gas flow rate, the HBr gas flow rate and the O2 gas flow rate is in the range of 1:5:1-1:7:
1.
10. The method for preparing a conductive contact hole according to claim 8, wherein: The SF6 gas flow rate ranges from 10 sccm to 20 sccm; The HBr gas flow rate ranges from 100 sccm to 200 sccm; The O 2 gas flow rate ranges from 3 sccm to 7 sccm.