Method for forming trench structure, and semiconductor process apparatus

Abstract

Provided in the present disclosure are a method for forming a trench structure, and a semiconductor process apparatus. The method comprises: performing a first etching step, involving: etching an exposed surface of a film layer to be etched to form an arc-shaped first trench at the top of said film layer, wherein the opening width of the first trench that is close to a mask layer is greater than that of a mask opening; performing a second etching step, involving: etching the inner side of the first trench to convert the first trench into a second trench by means of etching, wherein the second trench comprises an arc-shaped contour located at an upper portion and a slope-shaped contour located at a lower portion; and performing a third etching step, involving: etching the inner side of the second trench to form a third trench below the second trench, wherein the third trench is in communication with the second trench. Using the present solution to form a trench structure is conductive to controlling the inclination angle of a slope formed by the arc-shaped contour and the slope-shaped contour, thereby enabling the slope to meet the requirements of preventing tip discharge and preventing blockages during subsequent filling.

Description

Method for forming trench structure and semiconductor processing equipment TECHNICAL FIELD

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

[0002] In order to avoid the occurrence of tip discharge at the corner of the top of the trench and the occurrence of plugging phenomenon in the subsequent filling process, it is usually necessary to form a fillet or a slope on the top of the trench during the process of forming the trench structure. In the related art, the method for forming the trench structure includes: as shown in FIGS. 1A-1B, first, the area exposed by the mask opening 12A of the to-be-etched film layer 11 is etched to form a trench 11A in the to-be-etched film layer 11; as shown in FIGS. 1B-1C, then, the mask layer 12 is pulled back to expand the opening width W1 of the mask opening 12A to expose the corner 11B at the top of the trench 11A; as shown in FIGS. 1C-1D, then, the corner 11B exposed at the top of the trench 11A is etched to form a slope 11C at the top of the trench 11A. SUMMARY

[0003] The present application provides a method for forming a trench structure and a semiconductor processing equipment to solve the problem that the opening width of the mask opening limits the adjustment window size of the inclination angle of the slope and is not conducive to controlling the inclination angle of the slope in the related art.

[0004] The first aspect of the present application provides a method for forming a trench structure, comprising:

[0005] providing a substrate; the substrate includes a to-be-etched film layer and a mask layer which are arranged in layers, and the mask layer is provided with a mask opening which exposes part of the surface of the to-be-etched film layer;

[0006] performing a first etching step to etch the surface exposed by the to-be-etched film layer to form a first trench in the form of a circular arc at the top of the to-be-etched film layer; the opening width of the first trench close to the mask layer is greater than the opening width of the mask opening;

[0007] performing a second etching step to etch the inner side of the first trench to etch the first trench into a second trench, and the second trench includes a circular arc profile at the upper part and a slope profile at the lower part;

[0008] performing a third etching step to etch the inner side of the second trench to form a third trench below the second trench, and the third trench is in communication with the second trench.

[0009] In an embodiment, the adjustment window size of the inclination angle of the slope profile of the second trench is limited by the opening width of the first trench close to the mask layer.

[0010] In one embodiment, the process conditions of the first etching step include that the main etching gas is a sulfur-containing fluorine-containing gas, and the process conditions of the second etching step include that the main etching gas is a carbon-containing fluorine-containing gas.

[0011] In one embodiment, in the second etching step, the inclination angle of the ramp-shaped profile of the second trench is adjusted by controlling the size of the lower electrode power; and / or, the etching depth of the ramp-shaped profile of the second trench is adjusted by controlling the length of the etching time.

[0012] In one embodiment, the circular-arc-shaped profile and the ramp-shaped profile of the second trench form a slope at the top of the third trench, and the inclination angle of the slope is determined by the ratio between the etching depth of the second trench and the opening width of the first trench close to the mask layer, the etching depth of the second trench ranges from 20 nm to 60 nm, and the opening width of the first trench close to the mask layer ranges from 4 μm to 10 μm.

[0013] In one embodiment, the process conditions of the second etching step further include that the power range of the upper electrode power is 500 W to 2000 W, and the pressure range of the process chamber is 100 mTorr to 300 mTorr.

[0014] In one embodiment, the process conditions of the second etching step further include that the flow rate range of the oxygen is 100 sccm to 200 sccm.

[0015] In one embodiment, in the first etching step, at least one of the following is included:

[0016] The opening width of the first trench close to the mask layer is adjusted by controlling the upper electrode power;

[0017] The position of the first trench in the thickness direction of the film to be etched is adjusted by controlling the lower electrode power.

[0018] In one embodiment, the range of the upper electrode power is 1000 W to 5000 W, the pressure range of the process chamber is 50 mTorr to 200 mTorr, and the range of the lower electrode power is 0 W to 50 W.

[0019] The second aspect of the present application provides a semiconductor process equipment, including a process chamber, a gas inlet assembly, an upper electrode assembly, a lower electrode assembly, and a controller, the controller includes at least one processor and at least one memory, the memory stores a computer program, and the computer program is executed by the processor to implement the method for forming a trench structure according to any one of the above embodiments.

[0020] The advantages or beneficial effects of the above technical solution at least include: by first forming a circular arc-shaped first groove on top of the to-be-etched film layer, and making the opening width of the first groove closer to the mask layer larger than the opening width of the mask layer, and then etching the inner side of the first groove, the circular arc-shaped profile reserved on the outer side of the first groove can form the circular arc-shaped profile of the upper part of the second groove, and the inner side of the first groove is etched to form the slope-shaped profile of the lower part of the second groove. This etching method can ensure that the adjustment window size of the inclination angle of the slope-shaped profile of the lower part of the second groove is not limited by the opening width of the mask layer, and the overall inclination angle of the circular arc-shaped profile and the slope-shaped profile can be determined by adjusting the inclination angle of the slope-shaped profile, so that the adjustment window size of the overall inclination angle is also not limited by the opening width of the mask opening, which is beneficial to controlling the overall inclination angle of the circular arc-shaped profile and the slope-shaped profile, so as to meet the needs of preventing the occurrence of sharp-point discharge and preventing the occurrence of blockage in the subsequent filling process. In this way, after the third etching step is performed, the circular arc-shaped profile and the slope-shaped profile of the second groove can form the slope of the top of the third groove, and ensure that the slope can prevent the occurrence of sharp-point discharge at the top of the third groove and prevent the occurrence of blockage in the subsequent filling process. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application. In addition, the drawings and the description are not intended to limit the scope of the present application in any way.

[0022] FIGS. 1A-1D show a cross-sectional structure schematic diagram in a process of forming a trench structure according to the related art.

[0023] FIG. 2 shows a flowchart of a method for forming a trench structure according to an embodiment of the present application.

[0024] FIGS. 3A-3D show a cross-sectional structure schematic diagram in a process of forming a trench structure according to an embodiment of the present application.

[0025] FIG. 4 shows a structure schematic diagram of a semiconductor process equipment according to an embodiment of the present application. DETAILED DESCRIPTION

[0026] In the following, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0027] In the related art, as shown in FIGS. 1A-1D, in the process of forming the trench structure, due to the limited degree of side pushing of the mask layer 12, the opening width W1 of the mask opening 12A is small, and the opening width W1 of the mask opening 12A determines the adjustment window size of the inclination angle a of the slope 11C, thereby causing the adjustment window of the inclination angle a of the slope 11C to be small, which is not conducive to adjusting the size of the inclination angle a of the slope 11C, and cannot ensure that the inclination angle a of the slope 11C can meet the needs of preventing tip discharge and preventing the phenomenon of blocking.

[0028] To at least solve the above technical problems existing in the related art, the embodiments of the present application provide a method for forming a trench structure and a semiconductor process equipment. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0029] FIG. 2 shows a flowchart of a method for forming a trench structure according to an embodiment of the present application. FIGS. 3A-3D show schematic diagrams of a cross-sectional structure in the process of forming a trench structure according to an embodiment of the present application.

[0030] As shown in FIG. 2, the method for forming a trench structure includes the following steps S110-S140.

[0031] Step S110, referring to FIG. 3A, a substrate 10 is provided; the substrate 10 includes a to-be-etched film layer 11 and a mask layer 12 stacked and arranged, the mask layer 12 is provided with a mask opening 12A, and the mask opening 12A exposes part of the surface of the to-be-etched film layer 11. The material of the to-be-etched film layer 11 can be silicon (Si), and the to-be-etched film layer 11 can be a single-layer or multi-layer structure. The material of the mask layer 12 can be silicon oxide (SiO2) or silicon nitride (SiN).

[0032] Step S120, referring to FIGS. 3A-3B, a first etching step is performed to etch the exposed surface of the to-be-etched film layer 11 to form a circular-arc-shaped first trench 111 on the top of the to-be-etched film layer 11; the opening width W2 of the first trench 111 close to the mask layer 12 is greater than the opening width W1 of the mask opening 12A. The opening width W2 of the first trench 111 close to the mask layer 12 can be the maximum lateral dimension of the first trench 111. By etching the exposed surface of the to-be-etched film layer 11, the circular-arc-shaped first trench 111 can be formed below the mask opening 12A without side pushing the mask layer 12, and the opening width W2 of the first trench 111 close to the mask layer 12 is greater than the opening width W1 of the mask opening 12A, so that the opening width W2 of the first trench 111 close to the mask layer 12 is not limited by the opening width W1 of the mask opening 12A.

[0033] Step S130, please refer to FIG. 3B to FIG. 3C, a second etching step is performed to etch the inner side of the first groove 111 to etch the first groove 111 into a second groove 112, the second groove 112 includes a circular arc profile 112A at the upper portion and a slope profile 112B at the lower portion.

[0034] In the process of etching the inner side of the first groove 111, the outer side of the first groove 111 is protected by the mask layer 12 and is not etched, and the original circular arc profile can be retained. The inner side of the first groove 111 is etched into a slope profile. The retained circular arc profile constitutes the circular arc profile 112A at the upper portion of the second groove 112, and the etched slope profile constitutes the slope profile 112B at the lower portion of the second groove 112. It is easy to understand that the inner side of the first groove 111 refers to the portion of the first groove 111 away from the mask layer 12, and the sidewall constituting this portion is etched into a slope. The outer side of the first groove 111 refers to the portion of the first groove 111 close to the mask layer 12, and the sidewall constituting this portion is protected by the mask layer 12 and is not etched.

[0035] The adjustment window size of the inclination angle β of the slope profile 112B at the lower portion of the second groove 112 is determined by the opening width W2 of the first groove 111 close to the mask layer 12. Since the opening width W2 of the first groove 111 close to the mask layer 12 is greater than the opening width W1 of the mask opening 12A, the opening width W2 of the first groove 111 close to the mask layer 12 is not limited by the opening width W1 of the mask opening 12A, so that the adjustment window size of the inclination angle β of the slope profile 112B is not limited by the opening width W1 of the mask opening 12A. The adjustment window size of the inclination angle β of the slope profile 112B determines the ease of adjustment of the inclination angle β of the slope profile 112B. The larger the adjustment window, the easier it is to adjust the inclination angle β of the slope profile 112B. The inclination angle β of the slope profile 112B is the angle between the slope profile 112B and the surface of the to-be-etched film layer 11 facing the mask layer 12.

[0036] Step S140, please refer to FIG. 3C to FIG. 3D, a third etching step is performed to etch the inner side of the second groove 112 to form a third groove 113 below the second groove 112, and the third groove 113 is in communication with the second groove 112. The opening width of the third groove 113 is close to the opening width of the mask opening 12A.

[0037] Exemplarily, the circular-arc profile 112A and the slope profile 112B of the second groove 112 constitute a slope 11C at the top of the third groove 113, and the overall inclination angle a of the circular-arc profile 112A and the slope profile 112B constitutes the inclination angle a of the slope 11C, where the overall inclination angle a is the included angle between the line connecting the top end of the circular-arc profile 112A and the bottom end of the slope profile 112B and the surface of the film layer 11 facing the mask layer 12.

[0038] In the above scheme, by first forming the circular-arc first groove 111 on the top of the film layer 11 to be etched, and making the opening width W2 of the first groove 111 close to the mask layer 12 larger than the opening width W1 of the mask layer 12, and then etching the inner side of the first groove 111, the circular-arc profile remaining on the outer side of the first groove 111 can constitute the circular-arc profile 112A at the upper part of the second groove 112, and the inner side of the first groove 111 is etched to form the slope profile 112B at the lower part of the second groove 112. This etching method can ensure that the adjustment window size of the inclination angle β of the slope profile 112B at the lower part of the second groove 112 is not limited by the opening width W1 of the mask layer 12, and the overall inclination angle a of the circular-arc profile 112A and the slope profile 112B can be determined by adjusting the inclination angle β of the slope profile 112B, which makes the adjustment window size of the overall inclination angle a not limited by the opening width W1 of the mask opening 12A, and is beneficial to control the overall inclination angle a of the circular-arc profile 112A and the slope profile 112B to meet the needs of preventing sharp-end discharge and preventing blockage in the subsequent filling process. Thus, after the third etching step is performed, the circular-arc profile 112A and the slope profile 112B of the second groove 112 can constitute the slope 11C at the top of the third groove 113, and ensure that the slope 11C can prevent the top of the third groove 113 from appearing sharp-end discharge and prevent blockage in the subsequent filling process.

[0039] In one embodiment, as shown in FIGS. 3B and 3C, the adjustment window size of the inclination angle β of the slope profile 112B of the second groove 112 is limited by the opening width W2 of the first groove 111 close to the mask layer 12.

[0040] Exemplarily, the opening width W2 of the first trench 111 close to the mask layer 12 has a positive proportional relationship with the adjustment window size of the inclination angle β of the slope-shaped profile 112B of the second trench 112, that is, the larger the opening width W2 of the first trench 111 close to the mask layer 12, the larger the adjustment window, and vice versa. Wherein, the larger the adjustment window of the inclination angle β of the slope-shaped profile 112B, the easier to adjust the inclination angle α of the slope 11C composed of the arc-shaped profile 112A and the slope-shaped profile 112B of the second trench 112 by adjusting the inclination angle β of the slope-shaped profile 112B, so that the opening width W2 of the first trench 111 close to the mask layer 12 also has a positive proportional relationship with the adjustment window size of the inclination angle α of the slope 11C.

[0041] In an embodiment, the first etching step is substantially isotropic etching, and the second etching step is substantially anisotropic etching.

[0042] Exemplarily, referring to FIGS. 3A-3B, the first etching step is substantially isotropic etching, which means that the isotropic etching is dominant in the first etching step, and a small amount of anisotropic etching exists. The lateral etching consumption of the to-be-etched film layer 11 is slightly less than the longitudinal etching consumption of the to-be-etched film layer 11, so that the arc-shaped first trench 111 can be formed on the top of the to-be-etched film layer 11. Referring to FIGS. 3B-3C, the second etching step is substantially anisotropic etching, which means that the anisotropic etching is dominant in the second etching step, and a small amount of isotropic etching exists. In this way, in the process of etching the first trench 111 into the second trench 112, the outer side of the first trench 111 can be protected by the mask layer 12 and remain the original arc shape, and the inner side of the first trench 111 is etched into a slope-shaped profile to form the second trench 112.

[0043] In addition, it should be noted that, referring to FIGS. 1B-1C, the related art uses a wet etching process to push the mask layer 12 to expand the mask opening 12A. Since the process control ability of the wet etching process is poor, the opening width W1 of the mask opening 12A cannot be controlled, and thus the adjustment window size of the inclination angle α of the slope 11C cannot be controlled. Compared with the related art, referring to FIGS. 3A-3D, the embodiment of the present application uses an isotropic etching process, which is a dry etching process, and has a stronger process control ability, which can effectively control the opening width W2 of the first trench 111 close to the mask layer 12. Since the opening width W2 of the first trench 111 close to the mask layer 12 can determine the adjustment window size of the inclination angle α of the slope 11C, it is easier to control the adjustment window size of the inclination angle α of the slope 11C.

[0044] Further, referring to FIGS. 1B-1D, the related art uses a dry etching process to etch the corner 11B exposed by the mask opening 12A after the mask layer 12 is side pushed, so that the related art needs to alternately use a wet etching process and a dry etching process to form the slope 11C, resulting in a complex, high-cost, low-efficiency and difficult-to-perform etching process. Compared with the related art, the isotropic etching and the anisotropic etching used in the embodiments of the present application are both dry etching processes, and do not need to be alternately performed by different etching processes, thereby simplifying the etching process, reducing the process cost, improving the process efficiency and being easy to perform.

[0045] Further, the related art needs to displace and transport the substrate 10 between different process chambers to alternately perform the wet etching process and the dry etching process, so that dust or impurities are easily deposited on the substrate 10, which can cause defects or damage to the substrate 10. Compared with the related art, the isotropic etching and the anisotropic etching used in the embodiments of the present application can be in-situ etched in the same process chamber, so that the displacement and transportation of the substrate 10 can be omitted, and the defects or damage to the substrate 10 can be avoided.

[0046] In an embodiment, the process conditions of the first etching step include that the main etching gas is a sulfur-containing fluorine-containing gas, and the process conditions of the second etching step include that the main etching gas is a carbon-containing fluorine-containing gas.

[0047] For example, referring to FIGS. 3A-3B, the material of the film layer 11 to be etched can be silicon. Since the sulfur-containing fluorine-containing gas has good isotropic etching on silicon, the sulfur-containing fluorine-containing gas is selected as the main etching gas of the first etching step, so as to ensure that the first etching step is basically isotropic etching. For example, the sulfur-containing fluorine-containing gas can be sulfur hexafluoride (SF6). The lateral etching rate of the sulfur hexafluoride on the film layer 11 to be etched is greater than 5 μm / min, and the lateral etching rate and uniformity of the sulfur hexafluoride on the film layer 11 to be etched are better than those of a conventional etching gas. Therefore, the sulfur hexafluoride is selected as the main etching gas of the first etching step, so as to more easily control the first etching step to be basically isotropic etching. Since the carbon-containing fluorine-containing gas has good directionality on silicon etching, the carbon-containing fluorine-containing gas is selected as the main etching gas of the second etching step, so as to ensure that the second etching step is basically anisotropic etching. For example, the carbon-containing fluorine-containing gas can be carbon tetrafluoride (CF4). It should be noted that the sulfur-containing fluorine-containing gas and the carbon-containing fluorine-containing gas can be selected according to actual needs, and the embodiments of the present application do not limit this.

[0048] In one example, the process conditions of the first etching step further include an auxiliary etching gas. The auxiliary gas includes at least one of a xenon-containing gas, a nitrogen-containing gas, and a carbon-containing gas. Among them, at least one can be a gas or a mixed gas of multiple gases in the xenon-containing gas, the nitrogen-containing gas, and the carbon-containing gas. In the first etching step, when the exposed surface of the to-be-etched film layer 11 is etched by selecting a sulfur-containing and fluorine-containing gas as the main etching gas, the degree of lateral etching of the to-be-etched film layer 11 can be controlled by selecting at least one or a mixed gas of multiple gases in the xenon-containing gas, the nitrogen-containing gas, and the carbon-containing gas as the auxiliary etching gas.

[0049] In one embodiment, please refer to FIGS. 3B-3C, in the second etching step, the inclination angle β of the ramp-shaped profile 112B of the second trench 112 is adjusted by controlling the size of the lower electrode power; and / or, the etching depth of the ramp-shaped profile 112B of the second trench 112 is adjusted by controlling the length of the etching time. Among them, the etching depth of the ramp-shaped profile 112B of the second trench 112 can be the size of the ramp-shaped profile 112B in the thickness direction of the to-be-etched film layer 11, and the thickness direction of the to-be-etched film layer 11 is the direction from the side surface of the to-be-etched film layer 11 close to the mask layer 12 to the side surface of the to-be-etched film layer 11 away from the mask layer 12.

[0050] After the first etching step, the accumulated charges on the sidewall of the first trench 111 will attract the plasma. In the second etching step, the lower electrode power is used to control the bombardment energy of the plasma, and the lower electrode power has a positive proportional relationship with the bombardment energy of the plasma. Specifically, the greater the lower electrode power, the stronger the bombardment energy of the plasma, the stronger the ability of the plasma to offset the charge attraction, the straighter the etching of the inside of the first trench 111, the smaller the inclination angle β of the ramp-shaped profile 112B of the second trench 112 formed by etching, and the steeper the ramp-shaped profile 112B; on the contrary, the weaker the bombardment energy of the plasma, the weaker the ability of the plasma to offset the charge attraction, the greater the inclination angle β of the ramp-shaped profile 112B of the second trench 112 formed by etching, and the gentler the ramp-shaped profile 112B. In this way, by controlling the size of the lower electrode power, the inclination angle β of the ramp-shaped profile 112B of the second trench 112 can be adjusted, and then the inclination angle α of the ramp 11C can be controlled.

[0051] In the second etching step, when other process conditions remain unchanged, the longer the etching time, the deeper the etching depth of the ramp-shaped profile 112B of the second trench 112; the shorter the etching time, the shallower the etching depth of the ramp-shaped profile 112B of the second trench 112. Therefore, by controlling the length of the etching time, the etching depth of the ramp-shaped profile 112B of the second trench 112 can be adjusted.

[0052] The slope-shaped profile 112B of the second trench 112 can be controlled by controlling the power of the lower electrode in the second etching step, and the etching depth of the slope-shaped profile 112B can be controlled by controlling the etching time. Therefore, the slope-shaped profile 112B can be controlled by controlling the slope angle β and / or the etching depth of the slope-shaped profile 112B.

[0053] In one embodiment, referring to FIGS. 3B and 3C, the circular-arc-shaped profile 112A and the slope-shaped profile 112B of the second trench 112 form a slope 11C at the top of the third trench 113. The slope angle α of the slope 11C is determined by the ratio between the etching depth H of the second trench 112 and the opening width W2 of the first trench 111 close to the mask layer 12. The etching depth H of the second trench 112 ranges from 20 nm to 60 nm (including the end values), and the opening width W2 of the first trench 111 close to the mask layer 12 ranges from 4 μm to 10 μm (including the end values).

[0054] For example, the relationship between the slope angle α of the slope 11C and the ratio between the etching depth H of the second trench 112 and the opening width W2 of the first trench 111 close to the mask layer 12 can be expressed by the following formula (1):

[0055] In some embodiments, when the opening width W2 of the first trench 111 close to the mask layer 12 is 5 μm and the etching depth H of the second trench 112 is 52 nm, the slope angle α of the slope 11C is about 178.8°, and the slope 11C has a gentle profile and is not prone to tip discharge. When the first trench 111 is etched into the second trench 112, the opening width W2 of the first trench 111 close to the mask layer 12 is equal to the opening width W2 of the second trench 112 close to the mask layer 12.

[0056] In the above scheme, since the slope angle α of the slope 11C is determined by the ratio between the etching depth H of the second trench 112 and the opening width W2 of the first trench 111 close to the mask layer 12, by controlling the opening width W2 of the first trench 111 close to the mask layer 12 to be between 4 μm and 10 μm and controlling the etching depth H of the second trench 112 to be between 20 nm and 60 nm, the slope angle α of the slope 11C can be large, which is beneficial to ensure that the slope 11C has a gentle profile, thereby avoiding tip discharge and preventing the occurrence of the phenomenon of blocked opening in the subsequent filling process.

[0057] In one embodiment, the lower electrode power ranges from 10 W to 60 W, inclusive. For example, the lower electrode power can be any value from among 10 W, 20 W, and 60 W.

[0058] It is found through a large number of experiments that: please refer to FIG. 3D, if the lower electrode power is less than 10 W, the inclination angle β of the ramp-shaped profile 112B of the second trench 112 is too large, the topography of the ramp-shaped profile 112B is too flat, the included angle γ between the ramp-shaped profile 112B and the third trench 113 is too small, a new top corner is formed, and the top of the third trench 113 still has a problem of being prone to tip discharge; please refer to FIG. 3C, if the lower electrode power is greater than 60 W, the inclination angle β of the ramp-shaped profile 112B of the second trench 112 is too small, the topography of the ramp-shaped profile 112B is too steep, which will cause the inclination angle α of the slope 11C to be too small, and the slope 11C is also too steep, which cannot meet the requirement of preventing tip discharge.

[0059] The above scheme can make the lower electrode power in the second etching step be in a suitable power range by selecting the lower electrode power to be any value between 10 W and 60 W, which is conducive to controlling the ramp-shaped profile 112B of the second trench 112 to form a suitable inclination angle β, so that the topography of the ramp-shaped profile 112B is flat. This topography can make the top of the third trench 113 not prone to have sharp corners and protrusions, which can effectively prevent tip discharge at the top of the second trench 112 and prevent the phenomenon of clogging in the subsequent filling process.

[0060] In one embodiment, the process conditions of the second etching step further include that the upper electrode power ranges from 500 W to 2000 W, inclusive, and the pressure of the process chamber ranges from 100 mTorr to 300 mTorr, inclusive.

[0061] For example, in the second etching step, the pressure of the process chamber can be any value from among 100 mTorr, 150 mTorr, and 300 mTorr. The upper electrode power can be any value from among 500 W, 1000 W, and 2000 W.

[0062] The above scheme can control the main etching gas to dissociate high-density plasma, and make the ion flux of the plasma in a suitable range, so as to facilitate the plasma to perform longitudinal etching on the inner side of the first groove 111, and at the same time, perform lateral etching at a suitable etching rate; and by controlling the pressure range of the process chamber to be between 100 mTorr and 300 mTorr, the high pressure can increase the frequency of collision of high-density plasma, which is more helpful to generate scattering effect and lateral etching, so as to facilitate the lateral etching on the inner side of the first groove 111, thereby realizing the control of the plasma to simultaneously perform longitudinal etching and lateral etching on the inner side of the first groove 111 at a suitable etching rate, so as to form the slope-shaped profile 112B, and realize the etching of the first groove 111 into the second groove 112.

[0063] In an embodiment, referring to FIGS. 3B-3D, the process conditions of the second etching step further include that the flow rate of oxygen is in a range of 100 sccm-200 sccm (including the end point value). For example, the flow rate of oxygen can be any value in 100 sccm, 180 sccm and 200 sccm.

[0064] For example, in the process of etching the inner side of the first groove 111 by using the carbon-containing fluorine-containing gas, if a small amount of oxygen is added, the oxygen ions dissociated from the oxygen can be combined with the carbon ions dissociated from the carbon-containing fluorine-containing gas, so as to reduce the proportion of carbon ions in the etching process, and further reduce the generation of carbon-containing etching polymer, so that the etching of the inner side of the first groove 111 is relatively straight, which is helpful to form the slope-shaped profile 112B with a smaller inclination angle β; if a large amount of oxygen is added, the generated carbon-containing etching polymer is not enough to protect the sidewall of the inner side of the first groove 111, which will cause the lateral etching of the inner side of the first groove 111, so that the etching of the inner side of the first groove 111 is relatively inclined, which is helpful to form the slope-shaped profile 112B with a larger inclination angle β.

[0065] In the process of etching the inner side of the first groove 111 by using the carbon-containing fluorine-containing gas, by controlling the flow rate of oxygen to be between 100 sccm and 200 sccm, the addition of a large amount of oxygen can be used to ensure the formation of the slope-shaped profile 112B with a larger inclination angle β.

[0066] In an embodiment, referring to FIGS. 3A-3B, in the execution of the first etching step, at least one of the following is included:

[0067] The opening width W2 of the first groove 111 close to the mask layer 12 is adjusted by controlling the upper electrode power;

[0068] The first trench 111 is adjusted in the thickness direction of the film layer 11 to be etched by controlling the power of the lower electrode.

[0069] The upper electrode power is used to control the density of the plasma dissociated by the main etching gas in the first etching step. The higher the density of the plasma, the more conducive to the lateral etching of the film layer 11 to be etched. The upper electrode power has a positive correlation with the density of the plasma dissociated by the main etching gas. The upper electrode power can also be used to control the ion flux of the plasma. The ion flux of the plasma determines the etching rate of the film layer 11 to be etched by the plasma. The lower electrode power is used to accelerate the plasma so that the plasma has bombardment energy to pass through the mask opening 12A and move to the lower side of the mask layer 12.

[0070] It should be noted that, please refer to FIGS. 1B to 1D, the related art usually uses a wet etching process to push the mask layer 12 sideways. Since the process control ability of the wet etching process is poor, it is unable to control the opening width W1 of the mask opening 12A, and the opening width W1 of the mask opening 12A determines the lateral size of the slope 11C and the adjustment window size of the inclination angle a of the slope 11C, so the related art is unable to adjust the lateral size of the slope 11C and the adjustment window size of the inclination angle a of the slope 11C. Compared with the related art, please refer to FIGS. 3A to 3D, the above-mentioned scheme can adjust the high-density plasma dissociated by the main etching gas of the first etching step by controlling the size of the upper electrode power, and control the lateral etching rate of the high-density plasma to the film layer 11 to be etched, so as to adjust the opening width W2 of the first trench 111 close to the mask layer 12. The opening width W2 of the first trench 111 close to the mask layer 12 is equal to the lateral size of the slope 11C, and determines the adjustment window size of the inclination angle a of the slope 11C. Therefore, by adjusting the opening width W2 of the first trench 111 close to the mask layer 12, the lateral size of the slope 11C and the adjustment window size of the inclination angle a of the slope 11C can be adjusted. In addition, by controlling the lower electrode power, the bombardment energy of the plasma to the film layer 11 to be etched can be adjusted, which is helpful to control the plasma to pass through the mask opening 12A and move to the lower side of the mask layer 12, so as to form the first trench 111 under the mask layer 12 without affecting the appearance of the mask layer 12.

[0071] Further, in the first etching step, the method can further include: by controlling the pressure of the process chamber, the high-density plasma is more prone to perform lateral etching on the top of the film layer 11 to be etched. The pressure of the process chamber is used to control the plasma to generate scattering effect and lateral etching, so as to facilitate the lateral etching on the top of the film layer 11 to be etched, and the pressure of the process chamber also affects the density of the plasma. Therefore, by controlling the pressure of the process chamber, the high-density plasma is more prone to perform lateral etching on the top of the film layer 11 to be etched.

[0072] In an embodiment, the upper electrode power ranges from 1000 W to 5000 W (including the end point value), the pressure of the process chamber ranges from 50 mTorr to 200 mTorr (including the end point value), and the lower electrode power ranges from 0 W to 50 W (including the end point value).

[0073] For example, the pressure of the process chamber can be any value among 50 mTorr, 130 mTorr and 200 mTorr. The upper electrode power can be any value among 1000 W, 4000 W and 5000 W. The lower electrode power can be any value among 0 W, 20 W and 50 W.

[0074] The above scheme can achieve the following effects. By controlling the upper electrode power to be between 1000 W and 5000 W, the dissociation of the main etching gas into high-density plasma can be controlled, and the high-density plasma has a suitable ion flux, so as to effectively control the lateral etching rate of the plasma on the film layer 11 to be etched. By controlling the pressure of the process chamber to be between 50 mTorr and 200 mTorr, the high pressure can increase the frequency of collision between high-density plasma, which is more conducive to generating scattering effect and lateral etching, so as to facilitate the lateral etching on the top of the film layer 11 to be etched. By controlling the lower electrode power to be between 0 W and 50 W, the plasma has a lower bombardment energy, so that the plasma can pass through the mask opening 12A and move to the lower side of the mask layer 12. The lower electrode power applied to the lower electrode of the process chamber can provide a lower bias voltage to the process chamber. In this way, the high-density plasma can be used to perform isotropic etching on the film layer 11 to be etched below the mask layer 12, so as to form the first groove 111 below the mask layer 12, and the opening width W2 of the first groove 111 near the mask layer 12 is greater than the opening width W1 of the mask opening 12A, and the side wall of the first groove 111 has a smooth arc-shaped surface that is concave toward the bottom of the film layer 11 to be etched, that is, the profile of the first groove 111 is a circular arc.

[0075] In one embodiment, the first trench 111 has an opening width W2 close to the mask layer 12 ranging from 4 μm to 10 μm (including the end values); the vertical depth of the first trench 111 ranges from 50 nm to 100 nm (including the end values). For example, the opening width W2 of the first trench 111 close to the mask layer 12 can be any value among 4 μm, 5 μm and 10 μm. The vertical depth of the first trench 111 can be any value among 50 nm, 52 nm, 60 nm, 70 nm, 80 nm, 90 nm and 100 nm.

[0076] In one embodiment, the process conditions of the third etching step include: the pressure of the process chamber ranges from 10 mTorr to 80 mTorr (including the end values); the power of the upper electrode power ranges from 500 W to 2000 W (including the end values); the power of the lower electrode power ranges from 500 W to 1000 W (including the end values); the flow rate of the sulfur-containing fluorine-containing gas and the flow rate of the oxygen gas both range from 10 sccm to 100 sccm (including the end values).

[0077] In the third etching step, since the formation of the third trench 113 does not require high density of plasma, the pressure of the process chamber is controlled to be between 10 mTorr and 80 mTorr, so that the pressure of the process chamber is relatively small, and the density of the plasma is reduced to adapt to the process requirements. By controlling the upper electrode power to be between 500 W and 2000 W, the plasma has a suitable ion flux. By controlling the lower electrode power to be between 500 W and 1000 W, the plasma has a large bombardment energy, so that the plasma etches the inner side of the second trench 112 deeply and straightly, so as to form the third trench 113 with a deep depth and a straight sidewall below the second trench 112. In addition, by controlling the flow rate of the oxygen gas to be between 10 sccm and 100 sccm, a small amount of oxygen is added during the etching process to adjust the proportion of sulfur hexafluoride, so as to avoid the bending of the sidewall of the third trench 113.

[0078] Further, in the third etching step, at least one of chlorine and hydrogen bromide can be added to increase the selectivity to the mask layer 12, so that the etching rate of the to-be-etched film layer 11 is much faster than the etching rate of the mask layer 12, so as to form the third trench 113 as a deep trench below the second trench 112. The material of the mask layer 12 can be silicon oxide or silicon nitride, and the material of the to-be-etched film layer 11 can be silicon.

[0079] The method for forming a trench structure according to an embodiment of the present application is described in detail below with a specific example. The method for forming a trench structure includes a first etching step, a second etching step and a third etching step performed in sequence.

[0080] Table 1 Main process parameters of each step of forming the trench structure

[0081] Please refer to FIG. 3A to FIG. 3B, in the first etching step, the pressure of the process chamber is controlled between 50 mTorr and 200 mTorr, the upper electrode power is controlled between 1000 W and 5000 W, the lower electrode power is controlled between 0 W and 50 W, the flow rate of sulfur hexafluoride is controlled between 500 sccm and 2000 sccm, the temperature of the wafer carrier is controlled at 40℃, and the etching time is controlled between 10 s and 70 s. The first trench 111 can be formed on the top of the film to be etched 11, and the opening width W2 of the first trench 111 near the mask layer 12 is greater than the opening width W1 of the mask layer 12, and the opening width W2 of the first trench 111 near the mask layer 12 is between 4 μm and 10 μm.

[0082] Please refer to FIG. 3B to FIG. 3C, in the second etching step, the pressure of the process chamber is controlled between 100 mTorr and 300 mTorr, the upper electrode power is controlled between 500 W and 2000 W, the lower electrode power is controlled between 10 W and 60 W, the flow rate of carbon tetrafluoride (CF4) and oxygen (O2) is controlled between 100 sccm and 200 sccm, the temperature of the wafer carrier is controlled at 60℃, and the etching time is controlled between 10 s and 100 s. The first trench 111 can be etched into the second trench 112, so that the second trench 112 includes a circular arc profile 112A at the upper portion and a slope profile 112B at the lower portion, and the circular arc profile 112A and the slope profile 112B are smoothly connected, and the etching depth H of the second trench 112 is between 20 nm and 60 nm.

[0083] Please refer to FIG. 3C to FIG. 3D, in the third etching step, the pressure of the chamber is controlled between 10 mTorr and 80 mTorr, the upper electrode power is controlled between 500 W and 2000 W, the lower electrode power is controlled between 500 W and 1000 W, the flow rate of sulfur hexafluoride (SF6) is controlled between 10 sccm and 1000 sccm, the flow rate of oxygen is controlled between 10 sccm and 100 sccm, the flow rate of helium (He) is 135 sccm, the temperature of the wafer carrier is controlled at 60℃, and the etching time is controlled between 10 s and 300 s. The third trench 113 can be formed below the second trench 112, so that the circular arc profile 112A and the slope profile 112B of the second trench 112 jointly form the slope 11C at the top of the third trench 113.

[0084] FIG. 4 shows a structural schematic diagram of a semiconductor process equipment according to an embodiment of the present application.

[0085] As shown in FIG. 4, the semiconductor processing apparatus includes at least one process chamber, a transfer chamber, and a controller. The process chamber is in selective communication with the transfer chamber. The controller includes at least one processor and at least one memory having stored therein a computer program that, when executed by the processor, implements the method of any of the above embodiments.

[0086] As shown in FIG. 4, the semiconductor processing apparatus 200 can include a process chamber 20, a gas inlet assembly 20A, an upper electrode assembly 20B and a lower electrode assembly 20C, a gas exhaust assembly 20D, and a controller (not shown in FIG. 4). The controller includes at least one processor and at least one memory having stored therein a computer program that, when executed by the processor, implements the method of forming a trench structure of any of the above embodiments.

[0087] Exemplarily, the controller can be an upper computer or a lower computer. The controller can control a valve of the gas inlet assembly 20A to open to introduce a corresponding process gas into the process chamber 20. The controller can also control the opening degree of the valve of the gas inlet assembly 20A to control the flow rate of the process gas. The controller can also control the gas exhaust assembly 20D to exhaust the interior of the process chamber 20, for example, by controlling the opening degree of the valve of the gas exhaust assembly 20D or the rotation speed of the exhaust pump, to control the pressure in the process chamber 20, to discharge reaction byproducts, and the like.

[0088] The upper electrode assembly 20B can include a radio frequency coil 21, an upper radio frequency power source 23, and an upper matching device 25. The controller is further configured to control the upper radio frequency power source 23 to provide radio frequency power to the radio frequency coil 21 through the upper matching device 25, so that the radio frequency coil 21 excites the process gas in the process chamber 20 to generate plasma.

[0089] The lower electrode assembly 20C can include a wafer support device 22, a lower radio frequency power source 24, and a lower matching device 26. The controller is further configured to control the lower radio frequency power source 24 to provide radio frequency power to the wafer support device 22 through the lower matching device 26, to provide a radio frequency bias. The wafer support device 22 can be an electrostatic chuck, a mechanical chuck, or a vacuum chuck, for example. The wafer support device 22 is configured to support a wafer 100 having a substrate 10 disposed thereon.

[0090] The semiconductor processing apparatus 200 of the embodiments of the present application can be an inductively coupled plasma (ICP) apparatus or a capacitively coupled plasma (CCP) apparatus. The embodiments of the present application do not limit the type of the semiconductor processing apparatus 200.

[0091] It should be noted that since the semiconductor process equipment adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0092] In addition, in the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "stacked" and the like should be understood in a broad sense, for example, can be fixedly connected, can also be detachably connected, or integrated; can be directly connected, or indirectly connected through an intermediate medium; can be internal communication of two elements or mutual interaction relationship of two elements. For those skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.

[0093] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of forming a trench structure, characterized by, The method comprises the following steps: providing a substrate; the substrate comprises a to-be-etched film layer and a mask layer stacked, the mask layer is provided with a mask opening, and the mask opening exposes part of the surface of the to-be-etched film layer; performing a first etching step to etch the exposed surface of the to-be-etched film layer to form a first trench in the form of a circular arc on the top of the to-be-etched film layer; the opening width of the first trench near the mask layer is greater than the opening width of the mask opening; performing a second etching step to etch the inner side of the first trench to etch the first trench into a second trench, the second trench comprises a circular arc profile at the upper part and a slope profile at the lower part; performing a third etching step to etch the inner side of the second trench to form a third trench below the second trench, the third trench is in communication with the second trench.

2. The method of claim 1, wherein, The size of the adjustment window of the inclination angle of the slope profile of the second trench is limited by the opening width of the first trench near the mask layer.

3. The method of claim 1, wherein, The process conditions of the first etching step include that the main etching body is a sulfur-containing fluorine-containing gas, and the process conditions of the second etching step include that the main etching gas is a carbon-containing fluorine-containing gas.

4. The method of claim 1, wherein, In the second etching step, the inclination angle of the slope profile of the second trench is adjusted by controlling the size of the lower electrode power; and / or the etching depth of the slope profile of the second trench is adjusted by controlling the length of the etching time.

5. The method of claim 1, wherein, The circular arc profile and the slope profile of the second trench constitute a slope at the top of the third trench, and the inclination angle of the slope is determined by the ratio between the etching depth of the second trench and the opening width of the first trench near the mask layer, the etching depth of the second trench ranges from 20nm to 60nm, and the opening width of the first trench near the mask layer ranges from 4μm to 10μm.

6. The method of claim 4, wherein, The process conditions of the second etching step further include that the power range of the upper electrode power is 500W-2000W, and the pressure range of the process chamber is 100mTorr-300mTorr.

7. The method of claim 3, wherein, The process conditions of the second etching step further include that the flow range of oxygen is 100sccm-200sccm.

8. The method of claim 1, wherein, In the first etching step, at least one of the following is included: adjusting the opening width of the first trench near the mask layer by controlling the upper electrode power; adjusting the position of the first trench in the thickness direction of the to-be-etched film layer by controlling the lower electrode power.

9. The method of claim 8, wherein, The range of the upper electrode power is 1000W-5000W, the pressure range of the process chamber is 50mTorr-200mTorr, and the range of the lower electrode power is 0W-50W.

10. A semiconductor process apparatus, characterized by, The method comprises a process chamber, a gas inlet assembly, an upper electrode assembly, a lower electrode assembly and a controller, wherein the controller comprises at least one processor and at least one memory, the memory stores a computer program, and the computer program is executed by the processor to realize the method for forming a trench structure according to any one of claims 1-9.

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