Method for forming trench, method for manufacturing semiconductor device, and semiconductor device

Abstract

The application provides a trench forming method, a semiconductor device manufacturing method and a semiconductor device. The trench forming method comprises forming a first mask layer and a second mask layer above a substrate; wherein the first mask layer is provided with a first etching window and a second etching window penetrating through the first mask layer, the second mask layer covers at least the bottom of the second etching window and does not cover the first etching window, and the thickness of the second mask layer is less than the thickness of the first mask layer; and the second mask layer and the substrate are etched through the first etching window and the second etching window with the first mask layer as a mask to form first and second trenches with different depths below the first and second etching windows, respectively. The method simultaneously forms a double-trench structure with different depths by etching the substrate once, and the process flow is simple, and the double-trench manufacturing process is simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a trench forming method, a semiconductor device manufacturing method and a semiconductor device. BACKGROUND

[0002] Silicon carbide (SiC) is a new type of wide band gap semiconductor material, which has high thermal conductivity, high breakdown field strength, high saturation velocity and other advantages, and is very suitable for making high-temperature and high-power semiconductor devices. Silicon carbide-based power devices can greatly exert their high-temperature, high-frequency and low-loss characteristics, making them have great application prospects in high-voltage, high-temperature, high-frequency, high-power, strong radiation and other aspects, including trench metal oxide semiconductor field effect transistor (MOSFET), trench insulated gate bipolar transistor (IGBT) and other devices.

[0003] In the design of trench devices, it is often necessary to design trench structures of different depths (i.e., double-trench structures), but in the manufacturing process of double-trench structure devices, the commonly used method is to realize trench structures of different depths through a process flow of twice mask deposition, photolithography, substrate dry etching and mask removal, which has a long process flow and also brings challenges to the overlay capability of photolithography, and the overlay precision is low. SUMMARY

[0004] In view of the above problems, the present application provides a trench forming method, a semiconductor device manufacturing method and a semiconductor device, which solve the technical problems of long process flow and low overlay precision of double-trench structure in the prior art.

[0005] In a first aspect, the present application provides a trench forming method, comprising:

[0006] providing a substrate;

[0007] forming a first mask layer and a second mask layer above the substrate; wherein the first mask layer is provided with a first etching window and a second etching window penetrating through the first mask layer, the second mask layer covers at least the bottom of the second etching window and does not cover the first etching window, and the thickness of the second mask layer is less than the thickness of the first mask layer;

[0008] Etching the second mask layer at the bottom of the second etching window and the substrate under the first etching window and the second etching window simultaneously, to form a first groove and a second groove under the first etching window and the second etching window respectively, wherein the depth of the first groove is greater than the depth of the second groove.

[0009] According to the embodiments of the present application, optionally, in the method for forming the groove, the first mask layer and the second mask layer are formed above the substrate, including the following steps:

[0010] The first mask layer is formed above the substrate, and the first mask layer is subjected to a patterning process to form a first etching window and a second etching window penetrating through the first mask layer;

[0011] The second mask layer covering the first mask layer, the first etching window and the second etching window is formed, and the second mask layer is subjected to a patterning process to form a third etching window penetrating through the second mask layer; wherein the third etching window is arranged corresponding to the first etching window to expose the first etching window.

[0012] According to the embodiments of the present application, optionally, in the method for forming the groove, the first mask layer and the second mask layer are formed above the substrate, including the following steps:

[0013] The second mask layer is formed above the substrate, and the second mask layer is subjected to a patterning process to form a third etching window penetrating through the second mask layer;

[0014] The first mask layer covering the third etching window and the second mask layer is formed, and the first mask layer is subjected to a patterning process to form a first etching window and a second etching window penetrating through the first mask layer; wherein the first etching window is arranged corresponding to the third etching window to expose the third etching window.

[0015] According to the embodiments of the present application, optionally, in the method for forming the groove, the first mask layer is subjected to a patterning process to form a first etching window and a second etching window penetrating through the first mask layer, including the following steps:

[0016] The first photoresist covering the first mask layer is formed, and the first photoresist is subjected to a patterning process to form a first photoresist pattern;

[0017] The first mask layer is etched with the first photoresist pattern as a mask to form a first etching window and a second etching window penetrating through the first mask layer;

[0018] removing the remaining first photoresist.

[0019] According to the embodiment of the present application, optionally, in the method for forming the trench, the second mask layer is subjected to a patterning process to form a third etching window penetrating through the second mask layer, which comprises the following steps:

[0020] forming a second photoresist covering the second mask layer, and subjecting the second photoresist to a patterning process to form a second photoresist pattern;

[0021] taking the second photoresist pattern as a mask, and etching the second mask layer to form a third etching window penetrating through the second mask layer;

[0022] removing the remaining second photoresist.

[0023] According to the embodiment of the present application, optionally, in the method for forming the trench, the method further comprises:

[0024] removing the remaining first mask layer and the remaining second mask layer.

[0025] According to the embodiment of the present application, optionally, in the method for forming the trench, the material of the first mask layer is different from the material of the second mask layer.

[0026] According to the embodiment of the present application, optionally, in the method for forming the trench, the material of the first mask layer comprises silicon oxide.

[0027] According to the embodiment of the present application, optionally, in the method for forming the trench, the material of the second mask layer comprises silicon nitride or polycrystalline silicon.

[0028] In a second aspect, the present application provides a method for manufacturing a semiconductor device, which comprises:

[0029] providing a substrate;

[0030] forming a first mask layer and a second mask layer above the substrate; wherein the first mask layer is provided with a first etching window and a second etching window penetrating through the first mask layer, the second mask layer covers at least the bottom of the second etching window and does not cover the first etching window, and the thickness of the second mask layer is less than the thickness of the first mask layer;

[0031] taking the first mask layer and the second mask layer as masks, and etching the second mask layer at the bottom of the second etching window and the substrate below the first etching window and the second etching window to form a first trench and a second trench below the first etching window and the second etching window, respectively; wherein the depth of the first trench is greater than the depth of the second trench.

[0032] forming corresponding device structures in the first trench and the second trench, respectively.

[0033] According to the embodiments of the present application, optionally, in the method for manufacturing the semiconductor device, the device structure includes a gate structure, a source structure, or an isolation structure.

[0034] In a third aspect, the present application provides a semiconductor device manufactured by the method for manufacturing the semiconductor device according to any one of the second aspect.

[0035] By using the above technical solutions, at least the following technical effects can be achieved:

[0036] The present application provides a method for forming a trench, a method for manufacturing a semiconductor device, and a semiconductor device. The method for forming a trench includes forming a first mask layer and a second mask layer above a substrate; wherein the first mask layer is provided with a first etching window and a second etching window penetrating through the first mask layer, the second mask layer covers at least the bottom of the second etching window and does not cover the first etching window, and the thickness of the second mask layer is less than the thickness of the first mask layer; and etching the second mask layer and the substrate through the first etching window and the second etching window while taking the first mask layer as a mask to form a first trench and a second trench with different depths below the first etching window and the second etching window, respectively. This method performs one etching on the substrate to simultaneously form a double-trench structure with different depths, and the process flow is simple, thereby simplifying the manufacturing process of the double trench. This method can precisely control the depth, width, and spacing of the trench by controlling the thickness of the second mask layer, and has high registration accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with the specific embodiments described below, but do not constitute a limitation on the present application. In the drawings:

[0038] Figure 1 is a flowchart of a method for forming a trench according to an example embodiment of the present application;

[0039] Figure 2 is a cross-sectional structure diagram of a first intermediate structure formed by related steps of a method for forming a trench according to an example embodiment of the present application;

[0040] Figure 3 is a cross-sectional structure diagram of a second intermediate structure formed by related steps of a method for forming a trench according to an example embodiment of the present application;

[0041] Figure 4FIG. 3 is a cross-sectional view of a third intermediate structure formed by the steps of the trench formation method according to an exemplary embodiment of the present application;

[0042] Figure 5 FIG. 4 is a cross-sectional view of a fourth intermediate structure formed by the steps of the trench formation method according to an exemplary embodiment of the present application;

[0043] Figure 6 FIG. 5 is a cross-sectional view of a fifth intermediate structure formed by the steps of the trench formation method according to an exemplary embodiment of the present application;

[0044] Figure 7 FIG. 6 is a cross-sectional view of a trench structure formed by the trench formation method according to an exemplary embodiment of the present application;

[0045] Figure 8 FIG. 7 is a cross-sectional view of a first intermediate structure formed by the steps of another trench formation method according to an exemplary embodiment of the present application;

[0046] Figure 9 FIG. 8 is a cross-sectional view of a second intermediate structure formed by the steps of another trench formation method according to an exemplary embodiment of the present application;

[0047] Figure 10 FIG. 9 is a cross-sectional view of a third intermediate structure formed by the steps of another trench formation method according to an exemplary embodiment of the present application;

[0048] Figure 11 FIG. 10 is a cross-sectional view of a fourth intermediate structure formed by the steps of another trench formation method according to an exemplary embodiment of the present application;

[0049] Figure 12 FIG. 11 is a cross-sectional view of a trench structure formed by the trench formation method according to an exemplary embodiment of the present application;

[0050] Figure 13 FIG. 12 is a flowchart of a semiconductor device manufacturing method according to an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0051] The embodiments of the present application will be described in detail below with reference to the drawings and examples, so that the technical means applied by the present application to solve the technical problems and achieve the corresponding technical effects can be fully understood and implemented. The embodiments of the present application and various features in the examples can be combined with each other without conflict, and the technical solutions formed thereby are all within the protection scope of the present application. In the drawings, the sizes and relative sizes of the layers and regions may be exaggerated for clarity. The same reference signs represent the same elements throughout.

[0052] It should be understood that although the terms "first", "second", "third" and the like can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Therefore, the first element, component, region, layer or section discussed below can be represented as the second element, component, region, layer or section without departing from the teachings of the present application.

[0053] It should be understood that spatially relative terms, such as "above", "upper", "below", "lower", and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if a device in the figures is turned over, then the element or feature that is described as above other elements or features would then be oriented horizontally. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0054] The terms used herein are only for the purpose of describing specific embodiments and not as limitations of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of associated items.

[0055] In order to fully understand the present application, detailed structures and steps will be presented in the following description in order to illustrate the technical solutions proposed by the present application. The preferred embodiments of the present application are described in detail as follows, however, in addition to these detailed descriptions, the present application can have other embodiments.

[0056] Example One

[0057] The embodiment provides a trench forming method. Figure 1 FIG. 1 is a flowchart of a trench forming method according to an embodiment of the present application. Figures 2-7 FIG. 2 is a schematic diagram of a cross-sectional structure formed by related steps of the trench forming method according to an embodiment of the present application. Hereinafter, the detailed steps of an exemplary method of the trench forming method according to an embodiment of the present application will be described with reference to FIGS. 1-2. Figure 1 Figures 2-7

[0058] As shown in FIG. 1, the trench forming method according to the embodiment includes the following steps. Figure 1

[0059] Step S110: providing a substrate 11.

[0060] In the embodiment, the substrate 11 can be a silicon carbide substrate.

[0061] Step S120: forming a first mask layer 12 and a second mask layer 13 above the substrate 11; wherein the first mask layer 12 is provided with a first etching window 121 and a second etching window 122 penetrating through the first mask layer 12, the second mask layer 13 covers at least a bottom of the second etching window 122 and does not cover the first etching window 121, and a thickness of the second mask layer 13 is less than a thickness of the first mask layer 12.

[0062] In the embodiment, the step S120 includes the following steps.

[0063] S122: forming the first mask layer 12 above the substrate 11, and performing a patterning process on the first mask layer 12 to form the first etching window 121 and the second etching window 122 penetrating through the first mask layer 12, as shown in FIG. 2. Figure 2

[0064] S124: forming the second mask layer 13 covering the first mask layer 12, the first etching window 121 and the second etching window 122, and performing a patterning process on the second mask layer 13 to form a third etching window 131 penetrating through the second mask layer 13, as shown in FIG. 3; wherein the third etching window 131 is arranged in correspondence with the first etching window 121 to expose the first etching window 121. Figure 3 In the embodiment, the first etching window 121 and the second etching window 122 expose surfaces of the substrate 11 thereunder, the second mask layer 13 covers sidewalls and the bottom of the second etching window 122, and the third etching window 131 formed on the second mask layer 13 exposes the first etching window 121.

[0065] In the embodiment, the first etching window 121 and the second etching window 122 expose surfaces of the substrate 11 thereunder, the second mask layer 13 covers sidewalls and the bottom of the second etching window 122, and the third etching window 131 formed on the second mask layer 13 exposes the first etching window 121.​​​​

[0066] Before forming the first mask layer 12, a cleaning step of the substrate 11 is further included.

[0067] In step S122, the first mask layer 12 is patterned to form the first etching window 121 and the second etching window 122 through the first mask layer 12, including the following steps:

[0068] S122a: a first photoresist (not shown in the figure) covering the first mask layer 12 is formed, and the first photoresist is patterned to form a first photoresist pattern;

[0069] S122b: the first mask layer 12 is etched with the first photoresist pattern as a mask to form the first etching window 121 and the second etching window 122 through the first mask layer 12;

[0070] S122c: the remaining first photoresist is removed.

[0071] The first photoresist is used to protect the part of the first mask layer 12 which does not need to be etched in the etching process. The first mask layer 12 can be etched by a dry etching or wet etching process, and after the etching is completed, the remaining first photoresist is removed.

[0072] Further, in order to form a trench with a steep sidewall in the substrate 11 in the subsequent step, the first mask layer 12 is preferably etched by a dry etching process to form the first etching window 121 and the second etching window 122 with steep sidewalls.

[0073] In step S124, the second mask layer 13 is patterned to form the third etching window 131 through the second mask layer 13, including the following steps:

[0074] S124a: a second photoresist covering the second mask layer 13 is formed, and the second photoresist is patterned to form a second photoresist pattern 14, as shown in Figure 4

[0075] S124b: the second mask layer 13 is etched with the second photoresist pattern 14 as a mask to form the third etching window 131 through the second mask layer 13;

[0076] S124c: the remaining second photoresist is removed, as shown in Figure 5

[0077] ​​The second photoresist is used to protect the portion of the second mask layer 13 that does not require etching (i.e., the portion of the second mask layer 13 covering the second etching window 122, corresponding to the shallow trench position of the substrate 11) during the etching process, exposing the portion of the second mask layer 13 that needs etching (i.e., the portion of the second mask layer 13 covering the first etching window 121, corresponding to the deep trench position of the substrate 11). The portion of the second mask layer 13 covering the first etching window 121 can be etched using either dry etching or wet etching processes. After etching is completed, the remaining second photoresist is removed.

[0078] Furthermore, the materials of the first mask layer 12 and the second mask layer 13 may be different.

[0079] The material of the first mask layer 12 includes silicon oxide.

[0080] The material of the second mask layer 13 includes silicon nitride or polysilicon.

[0081] The difference between the materials of the first mask layer 12 and the second mask layer 13 can help determine the etching endpoint during the patterning process of the second mask layer 13.

[0082] Step S130: As Figure 6 As shown, using the first mask layer 12 and the second mask layer 13 as masks, the second mask layer 13 at the bottom of the second etching window 122 and the substrate 11 below the first etching window 121 and the second etching window 122 are etched simultaneously to form a first trench 111 and a second trench 112 below the first etching window 121 and the second etching window 122, respectively; wherein the depth of the first trench 111 is greater than the depth of the second trench 112.

[0083] Preferably, the second mask layer 13 at the bottom of the second etching window 122 and the substrate 11 below the first etching window 121 and the second etching window 122 can be etched using a dry etching process.

[0084] At the first etching window 121, the surface of the substrate 11 below it is directly exposed to the etching environment. After etching begins, the substrate 11 below it can be etched directly to form the first trench 111. At the second etching window 122, the substrate 11 below it is etched only after the second mask layer 13 at the bottom has been etched, forming the second trench 112. Therefore, the depth of the first trench 111 is greater than the depth of the second trench 112. In this step, two trenches of different depths are formed simultaneously through a one-step etching process. The process flow is simple, simplifying the fabrication process of the two trenches and reducing production costs.

[0085] Since the thickness of the second mask layer 13 is less than the thickness of the first mask layer 12, after the second mask layer 13 at the bottom of the second etching window 122 is etched, the first mask layer 12 still remains and can protect the substrate 11 below, thus playing a role of mask.

[0086] In addition, since the substrate 11 below is etched after the second mask layer 13 at the bottom of the second etching window 122 is etched, the thickness of the second mask layer 13 can be controlled to precisely control the depth of the first trench 111 and the second trench 112.

[0087] In the embodiment, the second mask layer 13 also covers the sidewall of the second etching window 122. In the dry etching process, due to the anisotropy of dry etching, the second mask layer 13 can protect the substrate 11 in the position of the sidewall of the second etching window 122 and the thickness range of the second mask layer 13. Therefore, by controlling the position and width of the second etching window 122 and the thickness of the second mask layer 13, the width of the second trench 112 and the distance between the second trench 112 and the first trench 111 can be controlled.

[0088] Further, in the scheme that the first etching window 121 and the second etching window 122 have steep sidewalls, after the dry etching process in step S130, the first trench 111 and the second trench 112 with steep sidewalls can be formed. Further, the width of the first trench 111 and the second trench 112 can be controlled.

[0089] Further, the material of the second mask layer 13 is different from the material of the substrate 11, which can be beneficial to the determination of the etching endpoint of the second mask layer 13 at the bottom of the second etching window 122 in step S130. Further, the depth of the first trench 111 and the second trench 112 can be precisely controlled.

[0090] Step S140: removing the remaining first mask layer 12 and second mask layer 13.

[0091] The obtained trench structure is as shown in Figure 7 .

[0092] The embodiment provides a semiconductor device manufacturing method, and a trench forming method comprises the following steps: forming a first mask layer 12 and a second mask layer 13 above a substrate 11; wherein the first mask layer 12 is provided with a first etching window 121 and a second etching window 122 penetrating through the first mask layer 12, the second mask layer 13 covers at least the bottom of the second etching window 122 and does not cover the first etching window 121, and the thickness of the second mask layer 13 is less than the thickness of the first mask layer 12; and etching the second mask layer 13 and the substrate 11 through the first etching window 121 and the second etching window 122 while taking the first mask layer 12 as a mask, so as to form first and second trenches 111 and 112 with different depths below the first and second etching windows 121 and 122 respectively. The method can form a double-trench structure with different depths by etching the substrate 11 once, and the process flow is simple, and the double-trench manufacturing process is simplified. The method can realize accurate control of the trench depth, width and spacing by controlling the thickness of the second mask layer 13, and the overlay accuracy is high.

[0093] Example Two

[0094] The embodiment provides another trench forming method. Figures 8-12 is a cross-sectional structure schematic diagram formed by related steps of a trench forming method shown in the embodiment of the application. Hereinafter, the detailed steps of an exemplary method of the trench forming method proposed in the embodiment of the application will be described with reference to Figures 8-12 .

[0095] The trench forming method of the embodiment comprises the following steps:

[0096] Step S210: providing a substrate 21.

[0097] The substrate 21 can be a silicon carbide substrate.

[0098] Step S220: forming a first mask layer 22 and a second mask layer 23 above the substrate 21; wherein the first mask layer 22 is provided with a first etching window 221 and a second etching window 222 penetrating through the first mask layer 22, the second mask layer 23 covers at least the bottom of the second etching window 222 and does not cover the first etching window 221, and the thickness of the second mask layer 23 is less than the thickness of the first mask layer 22.

[0099] In the embodiment, step S220 comprises the following steps:

[0100] S222: as shown in the figure, forming the second mask layer 23 above the substrate 21, and performing a patterning process on the second mask layer 23 to form a third etching window 231 penetrating through the second mask layer 23, as shown in the figure. Figure 8 Figure 9 ​​

[0101] S224: forming a first mask layer 22 covering the third etching window 231 and the second mask layer 23, and performing a patterning process on the first mask layer 22 to form a first etching window 221 and a second etching window 222 penetrating the first mask layer 22, as shown in Figure 10 FIG. 4; wherein the first etching window 221 is arranged corresponding to the third etching window 231 to expose the third etching window 231.

[0102] Wherein the first etching window 221 and the third etching window 231 expose the surface of the substrate 21 thereunder, and the second mask layer 23 covers the bottom of the second etching window 222.

[0103] Before forming the second mask layer 23, a cleaning step of the substrate 21 is further included.

[0104] In step S222, the patterning process is performed on the second mask layer 23 to form the third etching window 231 penetrating the second mask layer 23, including the following steps:

[0105] S222a: forming a second photoresist (not shown in the figure) covering the second mask layer 23, and performing a patterning process on the second photoresist to form a second photoresist pattern;

[0106] S222b: etching the second mask layer 23 with the second photoresist pattern as a mask to form the third etching window 231 penetrating the second mask layer 23;

[0107] S222c: removing the remaining second photoresist.

[0108] The second photoresist is used to protect the part of the second mask layer 23 that does not need to be etched (i.e. the part that needs to cover the substrate 22, corresponding to the shallow trench position of the substrate 21) in the etching process, and to expose the part of the second mask layer 23 that needs to be etched (i.e. the part that needs to expose the substrate 22, corresponding to the deep trench position of the substrate 21). The part of the second mask layer 23 that needs to be etched can be etched by a dry etching or wet etching process, and after the etching is completed, the remaining second photoresist is removed.

[0109] In step S224, the patterning process is performed on the first mask layer 22 to form the first etching window 221 and the second etching window 222 penetrating the first mask layer 22, including the following steps:

[0110] S224a: forming a first photoresist (not shown in the figure) covering the first mask layer 22, and performing a patterning process on the first photoresist to form a first photoresist pattern;

[0111] S224b: Using the first photoresist pattern as a mask, the first mask layer 22 is etched to form a first etching window 221 and a second etching window 222 that penetrate the first mask layer 22;

[0112] S224c: Remove the remaining first photoresist.

[0113] The first photoresist is used to protect the portion of the first mask layer 22 that does not require etching during the etching process. The first mask layer 22 can be etched using either dry etching or wet etching processes. After etching is complete, the remaining first photoresist is removed.

[0114] Furthermore, in order to form trenches with steep sidewalls in the substrate 21 in subsequent steps, it is preferable to etch the first mask layer 22 by a dry etching process to form a first etching window 221 and a second etching window 222 with steep sidewalls.

[0115] Furthermore, the materials of the first mask layer 22 and the second mask layer 23 may be different.

[0116] The material of the first mask layer 22 includes silicon oxide.

[0117] The material of the second mask layer 23 includes silicon nitride or polysilicon.

[0118] The difference between the materials of the first mask layer 22 and the second mask layer 23 can help determine the etching endpoint during the patterning process of the first mask layer 22.

[0119] Step S230: As Figure 11 As shown, using the first mask layer 22 and the second mask layer 23 as masks, the substrate 21 below the second mask layer 23 at the bottom of the second etching window 222 and below the first etching window 221 and the second etching window 222 are etched to form a first trench 211 and a second trench 212 below the first etching window 221 and the second etching window 222, respectively; wherein the depth of the first trench 211 is greater than the depth of the second trench 212.

[0120] Preferably, the second mask layer 23 at the bottom of the second etching window 222 and the substrate 21 below the first etching window 221 and the second etching window 222 can be etched using a dry etching process.

[0121] At the position of the first etching window 221, the surface of the substrate 21 under the first etching window 221 is directly exposed to the etching environment, and the etching of the substrate 21 under the first etching window 221 can be directly started to form the first trench 211. At the position of the second etching window 222, the etching of the substrate 21 under the second etching window 222 is not started until the etching of the second mask layer 23 at the bottom of the second etching window 222 is completed, to form the second trench 212. Therefore, the depth of the first trench 211 is greater than the depth of the second trench 212. In this step, the double trenches with different depths are formed by one etching process. The process flow is simple, the preparation process of the double trenches is simplified, and the production cost is reduced.

[0122] In this embodiment, the thickness of the second mask layer 23 is less than the thickness of the first mask layer 22. Therefore, after the etching of the second mask layer 23 at the bottom of the second etching window 222 is completed, the first mask layer 22 still remains and can protect the substrate 21 under the first mask layer 22, to play the role of the mask.

[0123] In addition, the etching of the substrate 21 under the second etching window 222 is not started until the etching of the second mask layer 23 at the bottom of the second etching window 222 is completed. Therefore, the thickness of the second mask layer 23 can be controlled to accurately control the depths of the first trench 211 and the second trench 212.

[0124] Further, in the scheme that the first etching window 221 and the second etching window 222 have steep sidewalls, the dry etching process in step S230 can form the first trench 211 and the second trench 212 with steep sidewalls. The width of the first trench 211 and the second trench 212 can be further controlled.

[0125] Further, the material of the second mask layer 23 is different from the material of the substrate 21, which can be beneficial to the determination of the etching endpoint of the second mask layer 23 at the bottom of the second etching window 222 in step S230. The depths of the first trench 211 and the second trench 212 can be further accurately controlled.

[0126] Step S240: removing the remaining first mask layer 22 and the second mask layer 23.

[0127] The obtained trench structure is shown in FIG. 2C. Figure 12

[0128] ​The embodiment provides a semiconductor device manufacturing method, and a trench forming method comprises the following steps: forming a first mask layer 22 and a second mask layer 23 above a substrate 21; wherein the first mask layer 22 is provided with a first etching window 221 and a second etching window 222 penetrating through the first mask layer 22, the second mask layer 23 covers at least the bottom of the second etching window 222 and does not cover the first etching window 221, and the thickness of the second mask layer 23 is less than the thickness of the first mask layer 22; and etching the second mask layer 23 and the substrate 21 through the first etching window 221 and the second etching window 222 while taking the first mask layer 22 as a mask, so as to form first and second trenches 211 and 212 with different depths below the first and second etching windows 221 and 222 respectively. The method can form a double-trench structure with different depths through one etching of the substrate 21, and the process flow is simple, and the double-trench manufacturing process is simplified. The method can realize accurate control of the trench depth by controlling the thickness of the second mask layer 23, and the register accuracy is high.

[0129] Example Three

[0130] Based on the embodiment one, the embodiment provides a semiconductor device manufacturing method.

[0131] As shown in Figure 13 , the semiconductor device manufacturing method comprises the following steps:

[0132] Step S310: providing a substrate 11.

[0133] The substrate 11 can be a silicon carbide substrate.

[0134] Step S320: forming a first mask layer 12 and a second mask layer 13 above the substrate 11; wherein the first mask layer 12 is provided with a first etching window 121 and a second etching window 122 penetrating through the first mask layer 12, the second mask layer 13 covers at least the bottom of the second etching window 122 and does not cover the first etching window 121, and the thickness of the second mask layer 13 is less than the thickness of the first mask layer 12.

[0135] In the embodiment, step S320 comprises the following steps:

[0136] S322: forming the first mask layer 12 above the substrate 11, and performing a patterning treatment on the first mask layer 12 to form the first etching window 121 and the second etching window 122 penetrating through the first mask layer 12, as shown in Figure 2 .

[0137] S324: as shown in Figure 3As shown, a second mask layer 13 covering the first mask layer 12, the first etching window 121 and the second etching window 122 is formed, and the second mask layer 13 is subjected to a patterning process to form a third etching window 131 penetrating the second mask layer 13; wherein the third etching window 131 is arranged in correspondence with the first etching window 121 to expose the first etching window 121.

[0138] As shown, a second mask layer 13 covering the first mask layer 12, the first etching window 121 and the second etching window 122 is formed, and the second mask layer 13 is subjected to a patterning process to form a third etching window 131 penetrating the second mask layer 13; wherein the third etching window 131 is arranged in correspondence with the first etching window 121 to expose the first etching window 121.

[0139] As shown, a second mask layer 13 covering the first mask layer 12, the first etching window 121 and the second etching window 122 is formed, and the second mask layer 13 is subjected to a patterning process to form a third etching window 131 penetrating the second mask layer 13; wherein the third etching window 131 is arranged in correspondence with the first etching window 121 to expose the first etching window 121.

[0140] As shown, a second mask layer 13 covering the first mask layer 12, the first etching window 121 and the second etching window 122 is formed, and the second mask layer 13 is subjected to a patterning process to form a third etching window 131 penetrating the second mask layer 13; wherein the third etching window 131 is arranged in correspondence with the first etching window 121 to expose the first etching window 121.

[0141] S322a: a first photoresist covering the first mask layer 12 is formed (not shown in the figure), and the first photoresist is subjected to a patterning process to form a first photoresist pattern;

[0142] S322b: the first mask layer 12 is etched with the first photoresist pattern as a mask to form the first etching window 121 and the second etching window 122 penetrating the first mask layer 12;

[0143] S322c: the remaining first photoresist is removed.

[0144] The first photoresist is used to protect the part of the first mask layer 12 that does not need to be etched in the etching process. The first mask layer 12 can be etched by a dry etching process or a wet etching process, and after the etching is completed, the remaining first photoresist is removed.

[0145] Further, in order to form a trench with a steep side wall in the substrate 11 in the subsequent step, the first mask layer 12 is preferably etched by a dry etching process to form the first etching window 121 and the second etching window 122 with steep side walls.

[0146] As shown, a second mask layer 13 covering the first mask layer 12, the first etching window 121 and the second etching window 122 is formed, and the second mask layer 13 is subjected to a patterning process to form a third etching window 131 penetrating the second mask layer 13; wherein the third etching window 131 is arranged in correspondence with the first etching window 121 to expose the first etching window 121.

[0147] S324a: a second photoresist covering the second mask layer 13 is formed, and the second photoresist is subjected to a patterning process to form a second photoresist pattern 14, as shown in Figure 4 ​

[0148] S324b: etching the second mask layer 13 with the second photoresist pattern 14 as a mask to form a third etching window 131 penetrating the second mask layer 13;

[0149] S324c: removing the remaining second photoresist, as shown in Figure 5

[0150] The second photoresist is used to protect the part of the second mask layer 13 which does not need to be etched (i.e. the part of the second mask layer 13 covering the second etching window 122, corresponding to the shallow trench position of the substrate 11) in the etching process, and to expose the part of the second mask layer 13 which needs to be etched (i.e. the part of the second mask layer 13 covering the first etching window 121, corresponding to the deep trench position of the substrate 11). The part of the second mask layer 13 covering the first etching window 121 can be etched by a dry etching or wet etching process. After the etching is completed, the remaining second photoresist is removed.

[0151] Further, the material of the first mask layer 12 and the material of the second mask layer 13 can be different.

[0152] The material of the first mask layer 12 includes silicon oxide.

[0153] The material of the second mask layer 13 includes silicon nitride or polysilicon.

[0154] The difference between the material of the first mask layer 12 and the material of the second mask layer 13 can be beneficial to the determination of the etching endpoint in the patterning process of the second mask layer 13.

[0155] Step S330: as shown in Figure 6 the first mask layer 12 and the second mask layer 13 as masks, etching the second mask layer 13 at the bottom of the second etching window 122 and the substrate 11 under the first etching window 121 and the second etching window 122 to form a first trench 111 and a second trench 112 under the first etching window 121 and the second etching window 122, respectively; wherein the depth of the first trench 111 is greater than the depth of the second trench 112.

[0156] Preferably, the dry etching process can be used to etch the second mask layer 13 at the bottom of the second etching window 122 and the substrate 11 under the first etching window 121 and the second etching window 122.

[0157] ​At the position of the first etching window 121, the surface of the substrate 11 below is directly exposed to the etching environment, and after the etching starts, the etching of the substrate 11 below can be directly performed to form the first groove 111. At the position of the second etching window 122, the etching of the substrate 11 below is not performed until the etching of the second mask layer 13 at the bottom is completed to form the second groove 112. Therefore, the depth of the first groove 111 is greater than the depth of the second groove 112. In this step, the two grooves with different depths are formed by one etching process. The process flow is simple, the preparation process of the two grooves is simplified, and the production cost is reduced.

[0158] In this embodiment, since the thickness of the second mask layer 13 is less than the thickness of the first mask layer 12, after the etching of the second mask layer 13 at the bottom of the second etching window 122 is completed, the first mask layer 12 still remains and can protect the substrate 11 below, thereby playing a role of a mask.

[0159] In addition, since the etching of the substrate 11 below is not performed until the etching of the second mask layer 13 at the bottom of the second etching window 122 is completed, the thickness of the second mask layer 13 can be controlled to accurately control the depths of the first groove 111 and the second groove 112.

[0160] In this embodiment, the second mask layer 13 also covers the sidewall of the second etching window 122. In the dry etching process, due to the anisotropy of the dry etching, the second mask layer 13 can protect the substrate 11 in the position of the sidewall of the second etching window 122 and the thickness range of the second mask layer 13. Therefore, by controlling the position and width of the second etching window 122 and the thickness of the second mask layer 13, the width of the second groove 112 and the distance between the second groove 112 and the first groove 111 can be controlled.

[0161] Further, in the scheme in which the first etching window 121 and the second etching window 122 have steep sidewalls, after the dry etching process in step S330, the first groove 111 and the second groove 112 with steep sidewalls can be formed. The width of the first groove 111 and the second groove 112 can be further controlled.

[0162] Further, the material of the second mask layer 13 is different from the material of the substrate 11, which can be beneficial to the determination of the etching endpoint of the second mask layer 13 at the bottom of the second etching window 122 in step S330. The depths of the first groove 111 and the second groove 112 can be further accurately controlled.

[0163] After step S330, the above method further includes: removing the remaining first mask layer 12 and the second mask layer 13.

[0164] The trench structure obtained is as shown in Figure 7

[0165] Step S340: forming corresponding device structures (not shown in the figure) in the first trench 111 and the second trench 112 respectively.

[0166] The device structures include a gate structure, a source structure, or an isolation structure.

[0167] The gate structure includes a gate insulating layer covering the sidewall and the bottom of the trench and a gate filling the trench, the gate being isolated from the substrate by the gate insulating layer.

[0168] The source structure is used for ion implantation of a source region and / or filling of a source metal.

[0169] The isolation structure is used for filling of an insulating material, and can be a field limiting ring structure.

[0170] Similarly, the preparation steps of the double-trench structure can also refer to the method in Embodiment Two, which will not be described here.

[0171] The embodiment provides a preparation method of a semiconductor device, which comprises the following steps: forming a first mask layer 12 and a second mask layer 13 above a substrate 11; wherein the first mask layer 12 is provided with a first etching window 121 and a second etching window 122 penetrating through the first mask layer 12, the second mask layer 13 covers at least the bottom of the second etching window 122 and does not cover the first etching window 121, and the thickness of the second mask layer 13 is less than the thickness of the first mask layer 12; etching the second mask layer 13 and the substrate 11 through the first etching window 121 and the second etching window 122 while taking the first mask layer 12 as a mask, so as to form a first trench 111 and a second trench 112 with different depths below the first etching window 121 and the second etching window 122 respectively; and forming corresponding device structures in the first trench and the second trench respectively. The method performs one etching on the substrate 11 and simultaneously forms double-trench structures with different depths, so that the process flow is simple and the preparation process of the double trench is simplified. The method can realize accurate control of the trench depth, width and spacing by controlling the thickness of the second mask layer 13, and has high overlay accuracy.

[0172] ​The above merely provides preferred embodiments of the present application, and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modified, equivalent replaced, improved, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application. Although the disclosed embodiments are as above, the content of the present application is only for the purpose of facilitating understanding of the present application, and is not intended to limit the present application. Any person skilled in the art, without departing from the spirit and scope of the present application, can make any modification and change in the implementation form and details, but the protection scope of the present application shall be subject to the range defined by the appended claims.

Claims

1. A method of forming a trench, characterized by, Comprising: providing a substrate; forming a first mask layer and a second mask layer above the substrate; wherein the first mask layer is provided with a first etching window and a second etching window penetrating the first mask layer, the second mask layer covers at least the bottom of the second etching window and does not cover the first etching window, and the thickness of the second mask layer is less than the thickness of the first mask layer; forming a first mask layer and a second mask layer above the substrate, comprising the following steps: forming a first mask layer, and performing a patterning process on the first mask layer to form a first etching window and a second etching window penetrating the first mask layer; forming a second mask layer, and performing a patterning process on the second mask layer to form a third etching window penetrating the second mask layer; wherein the third etching window is arranged corresponding to the first etching window; performing etching on the second mask layer at the bottom of the second etching window and the substrate below the first etching window and the second etching window with the first mask layer and the second mask layer as masks, to form a first trench and a second trench below the first etching window and the second etching window respectively; wherein the depth of the first trench is greater than the depth of the second trench.

2. The method of forming a trench according to claim 1, wherein forming a first mask layer and a second mask layer above the substrate, comprising the following steps: forming a first mask layer above the substrate, and performing a patterning process on the first mask layer to form a first etching window and a second etching window penetrating the first mask layer; forming a second mask layer covering the first mask layer, the first etching window and the second etching window, and performing a patterning process on the second mask layer to form a third etching window penetrating the second mask layer; wherein the third etching window is arranged corresponding to the first etching window to expose the first etching window.

3. The method of forming a trench according to claim 1, wherein forming a first mask layer and a second mask layer above the substrate, comprising the following steps: forming a second mask layer above the substrate, and performing a patterning process on the second mask layer to form a third etching window penetrating the second mask layer; forming a first mask layer covering the third etching window and the second mask layer, and performing a patterning process on the first mask layer to form a first etching window and a second etching window penetrating the first mask layer; wherein the first etching window is arranged corresponding to the third etching window to expose the third etching window.

4. The method of forming a trench according to claim 2 or 3, wherein performing a patterning process on the first mask layer to form a first etching window and a second etching window penetrating the first mask layer, comprising the following steps: forming a first photoresist covering the first mask layer, and performing a patterning process on the first photoresist to form a first photoresist pattern; performing etching on the first mask layer with the first photoresist pattern as a mask to form a first etching window and a second etching window penetrating the first mask layer; removing the remaining first photoresist.

5. The method of forming a trench according to claim 2 or 3, wherein performing a patterning process on the second mask layer to form a third etching window penetrating the second mask layer, comprising the following steps: forming a second photoresist covering the second mask layer, and performing a patterning process on the second photoresist to form a second photoresist pattern; performing etching on the second mask layer with the second photoresist pattern as a mask to form a third etching window penetrating through the second mask layer; removing the remaining second photoresist.

6. The method of forming a trench according to Claim 1, wherein Further comprising: removing the remaining first mask layer and the remaining second mask layer.

7. The method of forming a trench according to Claim 1, wherein The material of the first mask layer and the material of the second mask layer are different.

8. The method of forming a trench according to Claim 1, wherein The material of the first mask layer comprises silicon oxide.

9. The method of forming a trench according to Claim 1, wherein The material of the second mask layer comprises silicon nitride or polysilicon.

10. A method of manufacturing a semiconductor device, characterized by, Comprising: providing a substrate; forming a first mask layer and a second mask layer above the substrate; wherein the first mask layer is provided with a first etching window and a second etching window penetrating through the first mask layer, the second mask layer covers at least the bottom of the second etching window and does not cover the first etching window, and the thickness of the second mask layer is less than the thickness of the first mask layer; forming a first mask layer and a second mask layer above the substrate, comprising the following steps: forming a first mask layer, and performing a patterning process on the first mask layer to form a first etching window and a second etching window penetrating through the first mask layer; forming a second mask layer, and performing a patterning process on the second mask layer to form a third etching window penetrating through the second mask layer; wherein the third etching window is arranged corresponding to the first etching window; performing etching on the second mask layer at the bottom of the second etching window and on the substrate below the first etching window and the second etching window with the first mask layer and the second mask layer as masks to form a first trench and a second trench below the first etching window and the second etching window respectively; wherein the depth of the first trench is greater than the depth of the second trench; forming corresponding device structures in the first trench and the second trench respectively.

11. The method of producing a semiconductor device according to claim 10, wherein The device structures comprise gate structures, source structures or isolation structures.

12. A semiconductor device, characterized by comprising: The semiconductor device is prepared by the method of claim 10 or 11. The semiconductor device is prepared by the method of claim 10 or 11.

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