Side wall structure, forming method thereof and semiconductor device

Abstract

The invention provides a side wall structure, a forming method thereof and a semiconductor device, and the forming method of the side wall structure comprises the steps: providing a substrate which is provided with a gate structure; sequentially forming a first side wall material layer, a second side wall material layer and a third side wall material layer to cover the surface of the substrate and the outer wall of the gate structure along the shape, and forming a convex structure above the gate structure; forming a hard sacrificial material layer to cover the surface of the third side wall material layer in a conformal manner; executing a first anisotropic etching process to etch the hard sacrificial material layer, exposing the surface of the third side wall material layer, and reserving a part of the hard sacrificial material layer on the side wall of the convex structure; and executing a second anisotropic etching process to sequentially etch the third side wall material layer, the second side wall material layer and the first side wall material layer so as to form a side wall structure on the side wall of the gate structure. According to the invention, a thicker side wall structure can be easily formed.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a sidewall structure, a method for forming the same, and a semiconductor device. Background Art

[0002] A Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is one of the most basic devices in semiconductor manufacturing and is widely applicable to various chips. MOS transistors have characteristics such as high input impedance, low noise, large dynamic range, low power consumption, and easy integration, and can be used as amplifier circuits, voltage-controlled elements, electronic switches, or controllable rectifiers in chips, playing an important role.

[0003] In addition to the substrate, source electrode, drain electrode, gate electrode, etc., the sidewalls on both sides of the gate electrode also become one of the important structures of the MOS transistor. Although the sidewall structure seems simple, it plays an important role in electrical performance, reliability, process compatibility, etc. Therefore, how to fabricate the corresponding sidewall of the MOS transistor according to actual needs is very important. Summary of the Invention

[0004] To solve the above technical problems, a method for forming a sidewall structure provided by the present invention includes:

[0005] Providing a substrate, on which a gate structure is provided;

[0006] Successively forming a first sidewall material layer, a second sidewall material layer, and a third sidewall material layer to conformally cover the surface of the substrate and the outer wall of the gate structure, and forming a raised structure above the gate structure;

[0007] Forming a hard sacrificial material layer to conformally cover the surface of the third sidewall material layer;

[0008] Performing a first anisotropic etching process to etch the hard sacrificial material layer, exposing the surface of the third sidewall material layer, and retaining a part of the hard sacrificial material layer on the sidewall of the raised structure;

[0009] Performing a second anisotropic etching process to successively etch the third sidewall material layer, the second sidewall material layer, and the first sidewall material layer to form a sidewall structure on the sidewall of the gate structure.

[0010] Optionally, the material of the hard sacrificial material layer includes silicon nitride.

[0011] Optionally, the thickness of the hard sacrificial material layer is greater than or equal to 200 angstroms.

[0012] Optionally, the width of the sidewall structure is greater than or equal to 2000 angstroms.

[0013] Optionally, the sidewall structure is composed of the remaining third sidewall material layer, the second sidewall material layer, and the first sidewall material layer after performing the second dry etching process. The cross-sections of the remaining first sidewall material layer and the second sidewall material layer are stacked L-shaped and each includes a horizontal portion and a vertical portion. The remaining third sidewall material layer is located on the horizontal portion of the second sidewall material layer.

[0014] Optionally, the first anisotropic etching process includes a first dry etching process performed with the third sidewall material layer as the etching end layer.

[0015] Optionally, the materials of the first sidewall material layer and the third material layer include silicon oxide, and the material of the second sidewall material layer includes silicon nitride.

[0016] Optionally, the steps of performing the second anisotropic etching process further include: sequentially etching the third sidewall material layer, the second sidewall material layer, and the first sidewall material layer using respective corresponding dry etching processes and corresponding etching times to expose the surface of the substrate and the top wall of the gate structure, and removing the remaining hard sacrificial material layer.

[0017] Based on another aspect of the present invention, a sidewall structure is further provided. The sidewall structure is formed by the forming method as described above.

[0018] Based on another aspect of the present invention, a semiconductor device is further provided. The semiconductor device includes the sidewall structure as described above. Description of the Drawings

[0019] Those of ordinary skill in the art should understand that the provided drawings are used to better understand the present invention and do not constitute any limitation to the scope of the present invention. Among them:

[0020] Figures 1A to 1B is a schematic structural diagram of forming a sidewall structure in the related art;

[0021] Figure 2 is a flowchart of a method for forming a sidewall structure provided by an embodiment of the present application;

[0022] Figures 3A to 3G is a schematic structural diagram corresponding to the corresponding steps of the method for forming a sidewall structure provided by an embodiment of the present application.

[0023] Figures 1A to 1B In the figure: 10'-substrate; 11'-gate structure; 12'-first silicon oxide layer; 13'-silicon nitride layer; 14'-second silicon oxide layer; 15'-sidewall structure.

[0024] Figures 3A to 3G In the figure: 10 - substrate; 11 - gate structure; 12 - first sidewall material layer; 13 - second sidewall material layer; 14 - third sidewall material layer; 15 - protrusion structure; 21 - hard sacrificial material layer; 22 - sidewall structure. Detailed implementation mode

[0025] As described in the background art, in a related scenario, when developing a certain device on a high - voltage platform, the size of the device is the same as that of the device used on the low - voltage platform. It is found that the transistors of the manufactured device always fail in the Hot Carrier Injection (HCL) test. After analysis, it is confirmed that the above problem can be solved by increasing the width of the sidewall structure. The steps of forming the sidewall structure by the usual method can be, for example Figures 1A to 1B Schematic diagram. As Figure 1A shown, a gate structure 11' is provided on a substrate 10'. A first silicon oxide layer 12', a silicon nitride layer 13' and a second silicon oxide layer 14' are sequentially formed to conformally cover the surface of the substrate 10', the sidewalls and the top wall of the gate structure 11'; as Figure 1B shown, the second silicon oxide layer 14', the silicon nitride layer 13' and the first silicon oxide layer 12' are sequentially dry - etched, exposing the surface of the substrate 10' and the top wall of the gate structure 11', and using the first silicon oxide layer 12', the silicon nitride layer 13' and the second silicon oxide layer 14' remaining on the sidewalls of the gate structure 11' as the sidewall structure 15'.

[0026] In the method of stacking multiple layers of sidewall material layers (i.e., the first silicon oxide layer 12', the silicon nitride layer 13' and the second silicon oxide layer 14') and etching the multiple layers of sidewall material layers to form the sidewall structure 15', the thickness of the sidewall structure 15' is increased by increasing the thickness of the sidewall material layer. However, in practice, when continuously increasing the thickness of the sidewall material layer to form a wider sidewall structure 15', it is found that the above method has an obvious upper limit. For example, even if the thickness of the sidewall material layer is continuously increased, it is difficult to form a sidewall structure 15' with a thickness greater than 2000 angstroms. Moreover, when the stacking thickness of the multiple layers of sidewall material layers is too thick, it is not only unfavorable for the subsequent etching of the sidewall material layer, but also difficult to stably obtain a sidewall structure 15' with the expected width.

[0027] To this end, the present invention provides a sidewall structure, a method for forming the same, and a semiconductor device. The method for forming the sidewall structure includes: providing a substrate on which a gate structure is provided; sequentially forming a first sidewall material layer, a second sidewall material layer, and a third sidewall material layer conformally covering the surface of the substrate and the outer wall of the gate structure, and forming a protrusion structure above the gate structure; forming a hard sacrificial material layer conformally covering the surface of the third sidewall material layer; performing a first anisotropic etching process to etch the hard sacrificial material layer, exposing the surface of the third sidewall material layer, and retaining a part of the hard sacrificial material layer on the sidewall of the protrusion structure; performing a second anisotropic etching process to sequentially etch the third sidewall material layer, the second sidewall material layer, and the first sidewall material layer to form a sidewall structure on the sidewall of the gate structure. Compared with the method of directly etching multiple stacked sidewall material layers to form a sidewall, in this application, a hard sacrificial material layer is formed on the three sidewall material layers, and before etching the three sidewall material layers, the hard sacrificial material layer is etched separately, and the width of the hard sacrificial material layer remaining around the protrusion structure is used to control the width of the subsequent sidewall structure, so that a wider sidewall structure can be formed, breaking through the width limitation of directly etching multiple sidewall material layers to form a sidewall structure, and the thickness of the three sidewall material layers can also be reduced to simplify the process of etching the sidewall material layers.

[0028] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are all in a very simplified form and not drawn to scale, and are only used to facilitate and clearly assist in explaining the objectives of the embodiments of the present invention. In addition, the structures shown in the accompanying drawings are often part of the actual structures. In particular, the emphasis that each accompanying drawing needs to show is different, and sometimes different scales are used.

[0029] As used in the present invention, the singular forms "a", "an", and "the" include plural objects, the term "or" is generally used in the sense of including "and / or", the term "several" is generally used in the sense of including "at least one", the term "at least two" is generally used in the sense of including "two or more", and in addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", and "third" may explicitly or implicitly include one or at least two of such features, unless the content clearly indicates otherwise.

[0030] The embodiment of the present application provides a method for forming a sidewall structure.

[0031] Figure 2It is a flowchart of a method for forming a sidewall structure provided by an embodiment of the present application.

[0032] As Figure 2 shown, the method for forming a sidewall structure provided by an embodiment of the present application includes:

[0033] S01: Provide a substrate, on which a gate structure is provided;

[0034] S02: Sequentially form a first sidewall material layer, a second sidewall material layer, and a third sidewall material layer to conformally cover the surface of the substrate and the outer wall of the gate structure, and form a protrusion structure above the gate structure;

[0035] S03: Form a hard sacrificial material layer to conformally cover the surface of the third sidewall material layer;

[0036] S04: Perform a first anisotropic etching process to etch the hard sacrificial material layer, expose the surface of the third sidewall material layer, and retain a part of the hard sacrificial material layer on the sidewall of the protrusion structure;

[0037] S05: Perform a second anisotropic etching process to sequentially etch the third sidewall material layer, the second sidewall material layer, and the first sidewall material layer to form a sidewall structure on the sidewall of the gate structure.

[0038] Figures 3A to 3G It is a schematic structural diagram corresponding to the corresponding steps of the method for forming a sidewall structure provided by an embodiment of the present application. Hereinafter, the method for forming a sidewall structure provided by an embodiment of the present application will be described in detail in conjunction with Figures 3A to 3G First, please refer to

[0039] and perform step S01 to provide a substrate, on which a gate structure is provided. Figure 3A The substrate 10 can be, for example, at least one of the materials mentioned below: silicon, silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanide on insulator (S-SiGeOI), silicon germanide on insulator (SiGeOI), and germanium on insulator (GeOI), etc. In the embodiment of the present application, the material of the substrate 10 is described by taking silicon (silicon substrate) as an example.

[0040]

[0041] ​Among them, the gate structure 11 protrudes from the surface of the substrate 10. The substrate 10 regions on both sides of the gate structure 11 can be the source region and the drain region respectively, for forming corresponding source and drain electrodes. In some examples, the gate structure 11 can include a gate dielectric layer located on the surface of the substrate 10 and a gate conductive layer located on the gate dielectric layer. The gate dielectric layer can be a gate oxide layer, such as including silicon oxide and / or silicon oxynitride. The gate conductive layer can, for example, include polysilicon or doped polysilicon. In other examples, it is also feasible that the gate structure 11 is a dummy gate structure.

[0042] Next, please refer to Figure 3B , perform step S02 to sequentially form a first sidewall material layer 12, a second sidewall material layer 13, and a third sidewall material layer 14 conformally covering the surface of the substrate 10 and the outer wall of the gate structure 11, and form a raised structure 15 above the gate structure 11.

[0043] The first sidewall material layer 12 conformally covers the surface of the substrate 10 and the outer wall (sidewall and top wall) of the gate structure 11. The first sidewall material layer 12 can be a liner layer, used for buffering, reducing interface states, protecting the sidewall of the gate structure 11, etc. The second sidewall material layer 13 conformally covers the surface of the first sidewall material layer 12. The second sidewall material layer 13 can be a main isolation layer, used for electrically isolating the gate structure 11 and the source / drain, etc. The third sidewall material layer 14 conformally covers the surface of the second sidewall material layer 13. The third sidewall material layer 14 can be used to control the width between the gate structure 11 and the source / drain, reduce parasitic capacitance, etc. Among them, the material of the first sidewall material layer 12 can include silicon oxide. The thickness of the first sidewall material layer 12 is relatively thin, for example, 100 Å to 200 Å. The material of the second sidewall material layer 13 can include silicon nitride or doped silicon nitride (such as silicon oxynitride). The thickness of the second sidewall material layer 13 is greater than the thickness of the first sidewall material layer 12, for example, 200 Å to 400 Å. The material of the second sidewall material layer 13 can include silicon oxide or doped silicon oxide (such as silicon carbon oxide, silicon carbon oxynitride). The thickness of the third sidewall material layer 14 can be determined according to the preset width of the sidewall structure to be formed, ensuring that the sum of the thicknesses of the first sidewall material layer 12, the second sidewall material layer 13, and the third sidewall material layer 14 is at least close to (or greater than, equal to) the preset width of the sidewall structure to be formed (the width at its widest part). For example, in an example, the preset width of the sidewall structure to be formed is about 2100 Å. The thickness of the first sidewall material layer 12 can be, for example, about 150 Å. The thickness of the second sidewall material layer 13 can be, for example, about 300 Å. The thickness of the third sidewall material layer 14 can be, for example, about 1600 Å. It can be understood that the thickness of each sidewall material layer covering the sidewall part of the gate structure 11 may be less than the thickness of the part covering the surface of the substrate 10. The thickness in this embodiment refers to the thickness of the part of each sidewall material layer covering the surface of the substrate 10.

[0044] In the present application, for example, the first sidewall material layer 12, the second sidewall material layer 13, and the third sidewall material layer 14 can be sequentially formed by a furnace tube process to coat the outer wall of the gate structure 11. The first sidewall material layer 12, the second sidewall material layer 13, and the third sidewall material layer 14 that wrap the outer wall of the gate structure 11 bulge along with the gate structure 11 and serve as the protruding structure 15.

[0045] Next, please refer to Figure 3C , and perform step S03 to form a hard sacrificial material layer 21 conformally covering the surface of the third sidewall material layer 14.

[0046] The hard sacrificial material layer 21 can be any suitable hard material, such as the material used as a hard mask. The thickness of the hard sacrificial material layer 21 can be greater than or equal to 200 angstroms and can be determined according to the preset width of the sidewall structure to be formed, that is, the greater the preset width, the greater the thickness of the hard sacrificial material layer 21. The preset width of the sidewall structure is controlled by the thickness of the hard sacrificial material layer 21. In the present application, the material of the hard sacrificial material layer 21 can be silicon nitride and can be formed by a furnace tube process. In one example, the preset width of the sidewall structure to be formed is about 2100 angstroms. The thickness of the first sidewall material layer 12 can be, for example, about 150 angstroms, the thickness of the second sidewall material layer 13 can be, for example, about 300 angstroms, the thickness of the third sidewall material layer 14 can be, for example, about 1600 angstroms, and the thickness of the hard sacrificial material layer 21 can be, for example, about 300 angstroms.

[0047] Next, please refer to Figure 3D , and perform step S04 to perform a first anisotropic etching process to etch the hard sacrificial material layer 21, expose the surface of the third sidewall material layer 14, and retain a part of the hard sacrificial material layer 21 on the sidewalls of the protruding structure 15.

[0048] The first anisotropic etching process can be a dry etching process (the first dry etching process), and the hard sacrificial material layer 21 can be etched by means of etching endpoint control to remove the hard sacrificial material layer 21 above the substrate 10 and the gate structure 11, expose the surface of the third sidewall material layer 14, and ensure that a part of the hard sacrificial material layer 21 is retained on the sidewalls of the above-mentioned protruding structure 15 for controlling the width of the sidewall structure. The hard sacrificial material layer retained on the sidewalls of the protruding structure 15 can be in a ramp shape or an L shape and can cover a part or all of the sidewalls of the protruding structure 15. The width of the remaining hard sacrificial material layer 21 can be greater than or equal to the preset width of the sidewall structure to be formed. In other words, the width of the hard sacrificial material layer 21 remaining around the protruding structure 15 can be used to control the width of the subsequent sidewall structure.

[0049] When performing the above dry etching, the surface of the third sidewall material layer 14 can be exposed as the etching endpoint, and the etching can be stopped after reaching this etching endpoint. On the premise of ensuring that the top wall of the gate structure 11 and the third sidewall material layer 14 above the source region and the drain region on both sides of the gate structure 11 are basically exposed, over-etching is avoided from affecting the hard sacrificial material layer 21 remaining on both sides (around) of the convex structure 15. It is also feasible that the remaining hard sacrificial material layer 21 only covers a part of the sidewalls of the convex structure 15.

[0050] Next, step S05 is performed, and a second anisotropic etching process is performed to etch the third sidewall material layer 14, the second sidewall material layer 13, and the first sidewall material layer 12 in sequence to form a sidewall structure 22 on the sidewalls of the gate structure 11.

[0051] A dry etching process corresponding to each respective material and the corresponding etching time can be used to etch the third sidewall material layer 14, the second sidewall material layer 13, and the first sidewall material layer 12 in sequence to expose the surface of the substrate 10 and the top wall of the gate structure 11, and the remaining third sidewall material layer 14, second sidewall material layer 13, and first sidewall material layer 12 after the second dry etching process are used as the sidewall structure 22. The cross-sections of the remaining first sidewall material layer 12 and second sidewall material layer 13 are stacked L-shaped and each includes its respective horizontal part and vertical part. The remaining third sidewall material layer 14 is located on the horizontal part of the second sidewall material layer 13.

[0052] The steps of the above second anisotropic etching process can, for example, include: Please refer to Figure 3E , a dry etching process for the third sidewall material layer 14 can be performed to expose the surface of the second sidewall material layer 13, and the remaining part of the third sidewall material layer 14 is located on both sides of the second sidewall material layer 13 on the sidewalls of the gate structure 11, and the remaining third sidewall material layer 14 can be in a sloped shape.

[0053] Please refer to Figure 3F , a dry etching process for the second sidewall material layer 13 can be performed to expose the surface of the first sidewall material layer 12, and the remaining part of the second sidewall material layer 13 is located on both sides of the gate structure 11, and the remaining second sidewall material layer 13 is in an L shape. It can be understood that the aforementioned remaining third sidewall material layer 14 is partially etched in this dry etching process, and the remaining third sidewall material layer 14 is located on the horizontal part of the remaining second sidewall material layer 13.

[0054] Please refer to Figure 3G, a dry etching process can be performed on the first sidewall material layer 12 to expose the surface of the substrate 10, and a remaining part of the first sidewall material layer 12 is located on both sides of the gate structure 11. The remaining first sidewall material layer 12 is in an L shape. A second sidewall material layer 13 and a third sidewall material layer 14 are sequentially stacked on the remaining first sidewall material layer 12, and the first sidewall material layer 12, the second sidewall material layer 13, and the third sidewall material layer 14 remaining on both sides (around) of the gate structure 11 are used as the sidewall structure 22.

[0055] Compared with the method of forming a sidewall by stacking multiple layers of sidewall material layers and directly etching the multiple layers of sidewall material layers, in this application, a hard sacrificial material layer is formed on the three-layer sidewall material layer. Before etching the three-layer sidewall material layer, the hard sacrificial material layer is etched separately, and the width of the hard sacrificial material layer remaining around the convex structure is used to control the width of the subsequent sidewall structure, so that a wider sidewall structure can be formed, breaking through the width limitation of forming a sidewall structure by directly etching multiple layers of sidewall material layers, and the thickness of the three-layer sidewall material layer can also be reduced to simplify the process of etching the sidewall material layer.

[0056] The embodiment of this application also provides a sidewall structure, and this sidewall structure is formed by the method as described above.

[0057] The embodiment of this application also provides a semiconductor device, and this semiconductor device includes the sidewall structure as described above. This semiconductor device can be, for example, (applied to) memory devices such as DRAM and SRAM, image sensors, or logic processor devices, etc. The embodiment of this application does not impose special restrictions on the specific type of this semiconductor device.

[0058] In summary, the present invention provides a sidewall structure, a method for forming the same, and a semiconductor device. The method for forming the sidewall structure includes: providing a substrate with a gate structure disposed thereon; sequentially forming a first sidewall material layer, a second sidewall material layer, and a third sidewall material layer conformally covering the surface of the substrate and the outer wall of the gate structure, and forming a protrusion structure above the gate structure; forming a hard sacrificial material layer conformally covering the surface of the third sidewall material layer; performing a first anisotropic etching process to etch the hard sacrificial material layer, exposing the surface of the third sidewall material layer, and retaining a portion of the hard sacrificial material layer on the sidewalls of the protrusion structure; performing a second anisotropic etching process to sequentially etch the third sidewall material layer, the second sidewall material layer, and the first sidewall material layer to form a sidewall structure on the sidewalls of the gate structure. Compared with the method of stacking multiple sidewall material layers and directly etching the multiple sidewall material layers to form a sidewall, in this application, a hard sacrificial material layer is formed on the three sidewall material layers, and before etching the three sidewall material layers, the hard sacrificial material layer is etched separately, and the width of the hard sacrificial material layer remaining around the protrusion structure is used to control the width of the subsequent sidewall structure, so that a wider sidewall structure can be formed, breaking through the width limitation of directly etching multiple sidewall material layers to form a sidewall structure, and the thickness of the three sidewall material layers can also be reduced to simplify the process of etching the sidewall material layers.

[0059] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for forming a side wall structure, characterized in that, Comprising: Providing a substrate, on which a gate structure is provided; Successively forming a first sidewall material layer, a second sidewall material layer, and a third sidewall material layer to conformally cover the surface of the substrate and the outer wall of the gate structure, and forming a raised structure above the gate structure; Forming a hard sacrificial material layer to conformally cover the surface of the third sidewall material layer; Performing a first anisotropic etching process to etch the hard sacrificial material layer, exposing the surface of the third sidewall material layer, and retaining a part of the hard sacrificial material layer on the sidewall of the raised structure; Performing a second anisotropic etching process to successively etch the third sidewall material layer, the second sidewall material layer, and the first sidewall material layer to form a sidewall structure on the sidewall of the gate structure.

2. The method for forming the sidewall structure according to claim 1, wherein The material of the hard sacrificial material layer includes silicon nitride.

3. The method for forming the side wall structure according to claim 2, wherein The thickness of the hard sacrificial material layer is greater than or equal to 200 angstroms.

4. The forming method of the side wall structure according to claim 1, characterized in that The width of the sidewall structure is greater than or equal to 2000 angstroms.

5. The method for forming the sidewall structure according to claim 1, wherein The sidewall structure is composed of the remaining third sidewall material layer, the second sidewall material layer, and the first sidewall material layer after performing the second dry etching process. The profiles of the remaining first sidewall material layer and the second sidewall material layer are stacked L-shaped and each includes its respective horizontal portion and vertical portion. The remaining third sidewall material layer is located on the horizontal portion of the second sidewall material layer.

6. The forming method of the side wall structure according to claim 1, characterized in that, The first anisotropic etching process includes a first dry etching process performed with the third sidewall material layer as the etching end layer.

7. The method for forming the side wall structure according to claim 1, wherein The materials of the first sidewall material layer and the third material layer include silicon oxide, and the material of the second sidewall material layer includes silicon nitride.

8. The forming method of the side wall structure according to claim 7, characterized in that, The steps of performing the second anisotropic etching process further include: successively etching the third sidewall material layer, the second sidewall material layer, and the first sidewall material layer by using their respective corresponding dry etching processes and corresponding etching times to expose the surface of the substrate and the top wall of the gate structure, and removing the remaining hard sacrificial material layer.

9. A side wall structure, characterized in that, The sidewall structure is formed by the forming method as described in any one of claims 1 to 8.

10. A semiconductor device, characterized in that, The semiconductor device includes the sidewall structure as described in claim 1.

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