Method of fabricating a semiconductor structure

Abstract

The present disclosure provides a semiconductor structure manufacturing method, relates to the technical field of semiconductor, and is used for solving the technical problem that active regions are prone to tilting. The semiconductor structure manufacturing method comprises the following steps: forming a sacrifice structure on a substrate; etching the sacrifice structure and the substrate, so that multiple spaced active regions are formed in the substrate, and etching by-products are arranged between adjacent active regions, and the sacrifice structure forms a protrusion arranged on each active region; removing the etching by-products through wet etching, so that the portions of the adjacent protrusions away from the substrate are in contact and adhere to each other, the active regions connected with the protrusions are spaced apart and are in a tilting state; and removing the protrusions, so that the active regions are in a vertical state and the tilting state is released. The active regions are spaced apart, the diffusion of the reaction gas is facilitated, and the protrusions are removed completely by reacting with the protrusions, so that the active regions are prevented from remaining in the tilting state due to the adhesion of the remaining protrusions, and the tilting of the active regions is avoided.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of semiconductor technology, and in particular, to a manufacturing method of a semiconductor structure. BACKGROUND

[0002] With the development of semiconductor technology, the types of semiconductor structures are more and more, and the applications are more and more widely. For example, dynamic random access memory (DRAM) is widely used in various electronic devices because of its high storage density and fast read-write speed. The semiconductor structure includes a substrate, and a plurality of active areas (AA) are formed in the substrate in a spaced manner. However, the active areas are prone to tilting in the subsequent wet etching cleaning process and are difficult to recover. SUMMARY

[0003] In view of the above problems, the present disclosure provides a manufacturing method of a semiconductor structure to reduce the tilting of the active areas.

[0004] According to some embodiments, the present disclosure provides a manufacturing method of a semiconductor structure, which includes:

[0005] forming a sacrificial structure on a substrate;

[0006] etching the sacrificial structure and the substrate, forming a plurality of active areas in the substrate in a spaced manner, and having etching byproducts between adjacent active areas, and the sacrificial structure forms a protrusion arranged on each active area;

[0007] wet etching to remove the etching byproducts, and the portions of the adjacent protrusions away from the substrate are in contact and adhere to each other, and each active area corresponding to each protrusion is spaced apart and in a tilted state;

[0008] removing the protrusions, and each active area is out of the tilted state and recovers to be upright.

[0009] In some possible embodiments, the forming of the sacrificial structure on the substrate includes: forming at least two sacrificial layers arranged in a stacked manner on the substrate, and the at least two sacrificial layers form the sacrificial structure.

[0010] The etching of the sacrificial structure and the substrate includes: etching each sacrificial layer and the substrate to form the active areas and the protrusions, wherein the protrusions include at least two layers, and the number of the layers is less than or equal to the number of the sacrificial layers, and each layer corresponds to one sacrificial layer.

[0011] In some possible embodiments, the forming of the sacrificial structure on the substrate includes:

[0012] forming a first sacrificial layer on the substrate, forming a second sacrificial layer on the first sacrificial layer, and forming a third sacrificial layer on the second sacrificial layer, the third sacrificial layer, the second sacrificial layer and the first sacrificial layer forming the sacrificial structure;

[0013] etching the sacrificial structure and the substrate, comprising:

[0014] etching and removing the third sacrificial layer, part of the second sacrificial layer, part of the first sacrificial layer and part of the substrate to form the active region and the mesa, wherein the mesa comprises a first sub-layer and a second sub-layer, the first sub-layer comprises the remaining first sacrificial layer, and the second sub-layer comprises the remaining second sacrificial layer.

[0015] In some possible embodiments, etching and removing the third sacrificial layer, part of the second sacrificial layer, part of the first sacrificial layer and part of the substrate comprises:

[0016] etching the third sacrificial layer to form a preset pattern;

[0017] using the third sacrificial layer as a mask, etching the second sacrificial layer, the first sacrificial layer and the substrate, and etching and removing the third sacrificial layer in the process of etching the second sacrificial layer, the first sacrificial layer and the substrate to form the mesa and the active region.

[0018] In some possible embodiments, the material of the third sacrificial layer comprises polysilicon, and the material of the substrate comprises silicon.

[0019] In some possible embodiments, the etching byproduct is removed by wet etching, comprising:

[0020] the second sub-layer, the first sub-layer and the active region are inclined under the action of capillary force, adjacent second sub-layers are in contact and adhere to each other, each first sub-layer is spaced apart, and each active region is spaced apart.

[0021] In some possible embodiments, the material of the first sacrificial layer comprises oxide, and the material of the second sacrificial layer comprises nitride or oxynitride; or, the material of the first sacrificial layer comprises oxygen-rich silicon oxide compound, and the material of the second sacrificial layer comprises silicon-rich silicon oxide compound.

[0022] the etching byproduct is removed by wet etching, and part of the sidewall of the first sub-layer is also etched and removed, so that the sidewall of the first sub-layer is recessed in the sidewall of the second sub-layer.

[0023] In some possible embodiments, the etching solution of the wet etching comprises a diluted hydrofluoric acid solution.

[0024] In some possible embodiments, removing the protrusion and each of the active regions resumes the upright state from the tilted state comprises:

[0025] Step a: reacting a reaction gas with the second layer to form a reactant on a surface of the second layer;

[0026] Step b: heating the reactant, the reactant decomposes to form a plurality of gaseous products;

[0027] The steps a and b are repeated in sequence until the second layer is removed by reaction and the first layer is exposed, and the active regions resume the upright state from the tilted state.

[0028] In some possible embodiments, the first layer comprises silicon oxide, and the second layer comprises silicon nitride or silicon oxynitride; or, the first sacrificial layer comprises oxygen-rich silicon oxynitride, and the second sacrificial layer comprises silicon-rich silicon oxynitride.

[0029] The reaction gas comprises ammonia and hydrofluoric acid gas, and the reactant is heated to 100-200°C.

[0030] In some possible embodiments, the first sacrificial layer comprises carbon, and the second sacrificial layer comprises nitride or oxynitride.

[0031] Before removing the etching byproducts by wet etching, the method further comprises: removing part of the sidewall of the first layer by dry etching with a first etching gas, so that the sidewall of the first layer is recessed in the sidewall of the second layer, and part of the byproducts is removed by etching.

[0032] In some possible embodiments, removing the protrusion and each of the active regions resumes the upright state from the tilted state comprises:

[0033] Step a: reacting a reaction gas with the second layer to form a reactant on a surface of the second layer;

[0034] Step b: heating the reactant, the reactant decomposes to form a plurality of gaseous products;

[0035] The steps a and b are repeated in sequence until the second layer is removed by reaction and the first layer is exposed, and the active regions resume the upright state from the tilted state.

[0036] The first layer is removed by dry etching with a second etching gas, and the active regions are exposed.

[0037] In some possible embodiments, the first etching gas includes hydrogen and nitrogen, and the second etching gas includes hydrogen or helium.

[0038] In some possible embodiments, the second layer includes silicon nitride or silicon oxynitride, the reaction gas includes ammonia and hydrofluoric acid, and the reaction temperature is 100-200°C.

[0039] In some possible embodiments, the second layer covers the first layer in the orthographic projection of the substrate, and the distance between the edge of the orthographic projection of the second layer on the substrate and the edge of the orthographic projection of the first layer on the substrate is less than 1.5 nm.

[0040] The method for manufacturing a semiconductor structure provided by the embodiments of the present disclosure has at least the following advantages.

[0041] In the method for manufacturing a semiconductor structure provided by the embodiments of the present disclosure, the substrate and the sacrificial structure thereon are etched to form corresponding active regions and protrusions and etching byproducts between the active regions. The etching byproducts are removed by wet etching, and the portions of the adjacent protrusions away from the substrate are in contact and adhere to each other, and the active regions are spaced apart, so that the adjacent active regions are not adhered together and remain in the inclined state by the adhesion of the protrusions. By removing the protrusions, the active regions are released from the inclined state and restored to the upright state, avoiding the inclination of the active regions. Meanwhile, the active regions are spaced apart, and the oxidation treatment is not needed to form an oxide layer to achieve isolation, which can ensure the critical dimension of the active regions and avoid the loss of the critical dimension. In addition, the diffusion of the reaction gas and the reaction between the active regions and the protrusions facilitate the complete removal of the protrusions, avoiding the inclination of the active regions due to the adhesion of the remaining protrusions, and avoiding the inclination of the active regions. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 A process diagram for forming an active region in the related art;

[0043] Figure 2 A schematic diagram of an inclined active region in the related art;

[0044] Figure 3 A schematic diagram of an upright active region in the related art;

[0045] Figure 4 A schematic diagram of an inclined active region in the related art;

[0046] Figure 5 A Figure 4 A local enlarged view of position A in FIG. 1;

[0047] Figure 6Flowchart of a method of fabricating a semiconductor structure in an embodiment of the present disclosure;

[0048] Figure 7 Schematic diagram after forming a sacrificial structure in an embodiment of the present disclosure;

[0049] Figure 8 Schematic diagram after etching a third sacrificial layer in an embodiment of the present disclosure;

[0050] Figure 9 Schematic diagram after forming a bump in an embodiment of the present disclosure;

[0051] Figure 10 Schematic diagram of the bump contacting and adhering in an embodiment of the present disclosure;

[0052] Figure 11 Schematic diagram of the active region being restored to be upright in an embodiment of the present disclosure;

[0053] Figure 12 Process diagram of removing the first and second layers in an embodiment of the present disclosure;

[0054] Figure 13 Schematic diagram after etching a side wall of the first layer in an embodiment of the present disclosure;

[0055] Figure 14 Process diagram of removing the second layer in an embodiment of the present disclosure;

[0056] Figure 15 Schematic diagram after removing the second layer in an embodiment of the present disclosure.

[0057] Explanation of reference numerals:

[0058] 10 - substrate; 11 - active region;

[0059] 12 - etching byproduct; 13 - oxide layer;

[0060] 14 - contact groove; 20 - sacrificial structure;

[0061] 21 - first sacrificial layer; 22 - second sacrificial layer;

[0062] 23 - third sacrificial layer; 30 - bump;

[0063] 31 - first layer; 32 - second layer;

[0064] 33 - isolation groove; 40 - reactant. DETAILED DESCRIPTION

[0065] Reference is made to Figures 1 to 5In related technologies, the active region 11 is prone to tilting. The inventors discovered that the reason lies in the semiconductor structure fabrication process. (See [reference needed]) Figure 1 Typically, active regions 11 are first etched within the substrate 10, with etching byproducts 12 existing between the active regions 11. (See also...) Figure 2 Then, wet etching is used to remove etching byproducts 12. Due to capillary forces, adjacent active regions 11 tilt towards each other, and the surface of active regions 11 is covered with an oxide layer 13. The oxide layer 13 contacts and adheres to the active regions. The active regions 11 are then oxidized to thicken the oxide layer 13, preventing the active regions 11 from contacting each other. (See reference...) Figure 3 Then, the oxide layer 13 is removed by dry etching, so that the active region 11 is restored to an upright position.

[0066] During the above production process, please refer to Figure 4 and Figure 5 The etching gas has difficulty diffusing into the active regions 11, making it difficult to remove the oxide layer 13 between the active regions 11. The reacted substances are also not easily volatilized, making it difficult to completely remove the oxide layer 13, causing some active regions 11 to remain tilted. In addition, the oxide layer 13 is formed by the oxidation of the active regions 11 and is eventually removed, resulting in the loss of critical dimensions of the active regions 11.

[0067] This disclosure provides a method for fabricating a semiconductor structure in which protrusions are formed on the active regions. During wet etching to remove etching byproducts, adjacent protrusions, in regions away from the substrate, contact and adhere to each other, while the active regions are spaced apart. Adjacent active regions are not adhered together; instead, they maintain an inclined state due to the adhesion of the protrusions. This facilitates the diffusion of reactive gases and their reaction with the protrusions, allowing for complete removal of the protrusions and preventing the active regions from remaining tilted due to the adhesion of residual protrusions. Furthermore, it eliminates the need for oxidation treatment to form an oxide layer for isolation of the active regions, ensuring the critical dimensions of the active regions and preventing their loss.

[0068] To make the above-mentioned objects, features, and advantages of the embodiments of this disclosure more apparent and understandable, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0069] See Figure 6 This disclosure provides a method for fabricating a semiconductor structure, which includes the following steps:

[0070] Step S100: Form a sacrificial structure on the substrate.

[0071] Referring to Figure 7 The substrate 10 provides support and is used to form the active region 11, which can be made of a semiconductor material such as monocrystalline silicon, polycrystalline silicon, silicon on insulator (SOI), germanium, etc. The sacrificial structure 20 is formed on the substrate 10 and is used as a mask for etching the active region 11, and is also used to form the protrusions 30 arranged correspondingly on the substrate 10 to increase the overall height of the active region 11 and the corresponding protrusions 30. The sacrificial structure 20 can be a laminated structure to facilitate layer-by-layer processing of the sacrificial structure 20.

[0072] In some examples, the sacrificial structure 20 is formed on the substrate 10 by forming at least two sacrificial layers arranged in sequence on the substrate 10, and the at least two sacrificial layers form the sacrificial structure 20. In this way, one sacrificial layer is formed on the substrate 10, and then another sacrificial layer is formed on the sacrificial layer, and so on until all sacrificial layers are formed. These sacrificial layers are arranged in sequence on the substrate 10 to form the sacrificial structure 20, i.e., the sacrificial structure 20 includes two or more sacrificial layers arranged in sequence. The materials of the at least two sacrificial layers can be different from each other, or the materials of some sacrificial layers can be the same to facilitate separate processing of the desired sacrificial layers.

[0073] Step S200: etching the sacrificial structure and the substrate to form a plurality of active regions arranged at intervals in the substrate, and the adjacent active regions have etching byproducts, and the sacrificial structure forms protrusions arranged correspondingly on each active region.

[0074] Referring to Figures 7 to 9 The sacrificial structure 20 and the substrate 10 are etched to remove part of the sacrificial structure 20 and part of the substrate 10, and a plurality of active regions 11 arranged at intervals are formed in the substrate 10, and the contact grooves 14 surrounding each active region 11 are also formed in the substrate 10, and the adjacent active regions 11 have etching byproducts 12, i.e., the contact grooves 14 have etching byproducts 12 such as polymers.

[0075] The sacrificial structure 20 forms a plurality of protrusions 30 arranged at intervals, and each active region 11 has a corresponding protrusion 30 arranged thereon, and the corresponding active region 11 and the protrusion 30 are columnar. The sacrificial structure 20 also forms an isolation groove 33 surrounding each protrusion 30, and the isolation groove 33 penetrates the sacrificial structure 20. The isolation groove 33 is opposite and communicates with the contact groove 14, i.e., the gap between each protrusion 30 is opposite and communicates with the gap between each active region 11.

[0076] Forming at least two sacrificial layers on the substrate 10, the at least two sacrificial layers form the basis of an example of the sacrificial structure 20, etching the sacrificial structure 20 and the substrate 10, including: etching each sacrificial layer and the substrate 10 to form the active region 11 and the mesa 30, wherein the mesa 30 includes at least two layers, and the number of layers is less than or equal to the number of sacrificial layers, and each layer corresponds to a sacrificial layer.

[0077] Wherein the at least two sacrificial layers are etched to form the mesa 30, the mesa 30 has at least two layers, and the at least two layers are stacked in sequence, and each layer corresponds to a sacrificial layer, that is, each remaining sacrificial layer forms a layer of the mesa 30. The number of layers is less than or equal to the number of sacrificial layers. When at least one layer of the sacrificial layer is etched and removed as a whole away from the substrate 10, the number of layers is less than the number of sacrificial layers. When at least two sacrificial layers are etched and removed, the number of layers is equal to the number of sacrificial layers.

[0078] Step S300: wet etching to remove etching byproducts, and the adjacent mesas contact and adhere to each other in the area away from the substrate, and the active regions connected to each mesa are spaced apart and in a tilted state.

[0079] Referring to Figure 8 and Figure 9 , the etching byproducts 12 are removed by wet etching, and the etching liquid can include a dilute hydrofluoric acid (HF) solution. At the same time, due to the capillary force of the liquid, each active region 11 and the corresponding mesa 30 are tilted, and the tilting directions of the corresponding active region 11 and the mesa 30 are consistent (left-right direction shown in FIG. 6). Figure 10

[0080] The adjacent mesas 30 contact and adhere to each other in the area away from the substrate 10, and the active regions 11 connected to each mesa 30 are spaced apart and in a tilted state. The active region 11 and the corresponding connected mesa 30 are tilted as a whole under the action of the capillary force. The tilting height is certain, and when the tops of the adjacent mesas 30 adhere to each other, the active region 11 is in a tilted state, and there is still a certain distance between the active region 11 and the top of the mesa 30, so that there is still a gap between the adjacent active regions 11, that is, the adjacent active regions 11 are spaced apart.

[0081] ​In this way, on the one hand, the active region 11 is not in contact, and the active region 11 does not need to be oxidized to form an oxide layer to achieve isolation, so that the critical dimension (CD) of the active region 11 can be ensured, and the loss of the critical dimension can be avoided. On the other hand, the boss 30 is located above the active region 11, which facilitates the diffusion of the reaction gas and the reaction between the boss 30, facilitates the removal of the boss 30, and thus the active region 11 is released from the tilted state, and the active region 11 is prevented from remaining in the tilted state due to the adhesion of the remaining boss 30, and the tilting of the active region 11 is reduced.

[0082] Step S400: removing the boss, and each active region is released from the tilted state and restored to the upright state.

[0083] Referring to Figure 10 and Figure 11 , the boss 30 is removed, and the top surface of each active region 11 is exposed. Each active region 11 is not adhered together and remains in the tilted state by the adhesion of the boss 30, and when the boss 30 is removed, each active region 11 is released from the tilted state and restored to the upright state, and the tilting of the active region 11 is avoided. In the process of removing the etching byproduct 12 and removing the boss 30, the active region 11 is not consumed, and thus the loss of the critical dimension of the active region 11 is avoided.

[0084] In summary, in the method for manufacturing the semiconductor structure provided by the embodiment of the present disclosure, the substrate 10 and the sacrificial structure 20 thereon are etched to form the corresponding connected active region 11 and boss 30, and the etching byproduct 12 located between the active regions 11. The etching byproduct 12 is removed by wet etching, the adjacent boss 30 is in contact and adhered to the part of the region of the substrate 10, and each active region 11 is spaced apart, so that the adjacent active regions 11 are not adhered together and remain in the tilted state by the adhesion of the boss 30. By removing the boss 30, each active region 11 is released from the tilted state and restored to the upright state, and the tilting of the active region 11 is avoided. At the same time, each active region 11 is spaced apart, and the active region 11 does not need to be oxidized to form an oxide layer to achieve isolation, so that the critical dimension of the active region 11 can be ensured, and the loss of the critical dimension can be avoided. Furthermore, the diffusion of the reaction gas and the reaction between the boss 30 are facilitated, the boss 30 is completely removed, and the active region 11 is prevented from remaining in the tilted state due to the adhesion of the remaining boss 30, and the tilting of the active region 11 is avoided.

[0085] In some possible examples, referring to Figure 7The forming of the sacrificial structure 20 on the substrate 10 comprises: forming a first sacrificial layer 21 on the substrate 10, forming a second sacrificial layer 22 on the first sacrificial layer 21, and forming a third sacrificial layer 23 on the second sacrificial layer 22, the third sacrificial layer 23, the second sacrificial layer 22 and the first sacrificial layer 21 form the sacrificial structure 20. That is, in the direction away from the substrate 10, the sacrificial structure 20 comprises the first sacrificial layer 21, the second sacrificial layer 22 and the third sacrificial layer 23 which are sequentially stacked, and the first sacrificial layer 21, the second sacrificial layer 22 and the third sacrificial layer 23 can be formed by a deposition process.

[0086] Correspondingly, referring to Figure 8 , etching the sacrificial structure 20 and the substrate 10 comprises: etching and removing the third sacrificial layer 23, part of the second sacrificial layer 22, part of the first sacrificial layer 21 and part of the substrate 10, to form the active region 11 and the mesa 30, wherein the mesa 30 comprises a first sub-layer 31 and a second sub-layer 32, the first sub-layer 31 comprises the remaining first sacrificial layer 21, and the second sub-layer 32 comprises the remaining second sacrificial layer 22.

[0087] Referring to Figures 7 to 9 , when etching the third sacrificial layer 23, the second sacrificial layer 22, the first sacrificial layer 21 and the substrate 10, all of the third sacrificial layer 23, part of the second sacrificial layer 22, part of the first sacrificial layer 21 and part of the substrate 10 are removed, that is, the third sacrificial layer 23 is completely consumed and removed in the etching process, the remaining substrate 10 forms the active region 11, and the remaining first sacrificial layer 21 and the remaining second sacrificial layer 22 form the mesa 30.

[0088] The mesa 30 comprises the first sub-layer 31 arranged on the active region 11 and the second sub-layer 32 arranged on the first sub-layer 31, the first sub-layer 31 corresponds to the remaining first sacrificial layer 21, and the second sub-layer 32 corresponds to the remaining second sacrificial layer 22, that is, the remaining first sacrificial layer 21 forms the first sub-layer 31, and the remaining second sacrificial layer 22 forms the second sub-layer 32. In the etching process of the third sacrificial layer 23, the second sacrificial layer 22, the first sacrificial layer 21 and the substrate 10, etching by-products 12 are formed, and most of the etching by-products 12 are formed by etching the substrate 10 and are located between the active regions 11, for example, adhering to the surface of the active region 11.

[0089] In some possible implementation manners, as shown in Figure 7 and Figure 8 , etching and removing the third sacrificial layer 23, part of the second sacrificial layer 22, part of the first sacrificial layer 21 and part of the substrate 10 comprises: etching the third sacrificial layer 23 to form a preset pattern; taking the third sacrificial layer 23 as a mask, etching the second sacrificial layer 22, the first sacrificial layer 21 and the substrate 10, and etching and removing the third sacrificial layer 23 in the process of etching the second sacrificial layer 22, the first sacrificial layer 21 and the substrate 10 to form the mesa 30 and the active region 11.

[0090] Among them, such as Figure 8 As shown, the third sacrificial layer 23 is etched to remove a portion of it, forming a preset pattern on the third sacrificial layer 23 and exposing a portion of the surface of the second sacrificial layer 22. Using the remaining third sacrificial layer 23 as a mask, the second sacrificial layer 22, the first sacrificial layer 21, and the substrate 10 are etched to transfer the preset pattern of the third sacrificial layer 23 into the second sacrificial layer 22, the first sacrificial layer 21, and the substrate 10. Furthermore, during the etching of the second sacrificial layer 22, the first sacrificial layer 21, and the substrate 10, the remaining third sacrificial layer 23 is simultaneously etched away, i.e., all of the third sacrificial layer 23 is removed, leaving a portion of the second sacrificial layer 22 and a portion of the first sacrificial layer 21 to form the second layer 32 and the first layer 31, respectively.

[0091] For example, the material of the third sacrificial layer 23 includes polysilicon, and the material of the substrate 10 includes silicon. That is, the material of the third sacrificial layer 23 is the same as the material of the substrate 10. The remaining third sacrificial layer 23 is etched away at the same time as the substrate 10. The third sacrificial layer 23 serves as a mask and does not need to be removed separately. The thicknesses of the third sacrificial layer 23, the second sacrificial layer 22, and the first sacrificial layer 21 can be determined according to the specific process.

[0092] In some other possible examples, the sacrificial structure 20 is formed on the substrate 10, including: forming a first sacrificial layer 21 on the substrate 10, forming a second sacrificial layer 22 on the first sacrificial layer 21, and the second sacrificial layer 22 and the first sacrificial layer 21 forming the sacrificial structure 20.

[0093] Accordingly, etching the sacrificial structure 20 and the substrate 10 includes: etching away a portion of the second sacrificial layer 22, a portion of the first sacrificial layer 21 and a portion of the substrate 10 to form an active region 11 and a boss 30, wherein the boss 30 includes a first layer 31 and a second layer 32, the first layer 31 includes the remaining first sacrificial layer 21 and the second layer 32 includes the remaining second sacrificial layer 22.

[0094] See Figure 9 and Figure 10 In the example where the boss 30 includes a first layer 31 and a second layer 32, wet etching removes the etching byproduct 12, including: wet etching removes the etching byproduct 12, the second layer 32, the first layer 31 and the active region 11 are tilted under the action of capillary force, adjacent second layers 32 are in contact and adhere to each other, each first layer 31 is spaced apart, and each active region 11 is spaced apart.

[0095] The etching by-products 12 are removed by wet etching to clean the active regions 11 and the protrusions 30. Under the capillary force, the adjacent second sub-layers 32 are in contact and adhere to each other, the adjacent first sub-layers 31 are spaced apart, and the adjacent active regions 11 are spaced apart. With the height of the active regions 11, the first sub-layers 31 and the second sub-layers 32 being constant, the second sub-layers 32 adhere to each other, the first sub-layers 31 are separated, and the distance between the active regions 11 is increased to ensure that the active regions 11 do not adhere to each other.

[0096] To avoid the adjacent first sub-layers 31 from being in contact and adhering to each other, in some examples, the etching of the first sub-layers 31 can be performed simultaneously or prior to the removal of the etching by-products 12 by wet etching. The etching of the first sub-layers 31 can be performed to recess the sidewalls of the first sub-layers 31 from the sidewalls of the second sub-layers 32, so that the critical dimension between the adjacent first sub-layers 31 is greater than the critical dimension between the adjacent second sub-layers 32, i.e., the distance between the adjacent first sub-layers 31 is greater than the distance between the adjacent second sub-layers 32. In this way, when the adjacent second sub-layers 32 are in contact and adhere to each other, the first sub-layers 31 are connected below the second sub-layers 32, and the distance between the adjacent first sub-layers 31 is greater, so that the adjacent first sub-layers 31 are less likely to be in contact.

[0097] In some possible implementations, as shown in Figure 9 and Figure 10 , the first sacrificial layer 21 can be made of an oxide, and the second sacrificial layer 22 can be made of a nitride or an oxynitride; or, the first sacrificial layer 21 can be made of an oxygen-rich silicon oxide compound, and the second sacrificial layer 22 can be made of a silicon-rich silicon oxide compound. Correspondingly, the etching of the first sub-layers 31 can be performed simultaneously with the removal of the etching by-products 12 by wet etching, so that the sidewalls of the first sub-layers 31 are recessed from the sidewalls of the second sub-layers 32.

[0098] For example, the first sacrificial layer 21 can be made of silicon oxide, and the second sacrificial layer 22 can be made of silicon nitride or silicon oxynitride. Or, the first sacrificial layer 21 can be made of oxygen-rich silicon oxynitride (Oxygen-rich SiO x N y ), and the second sacrificial layer 22 can be made of silicon-rich silicon oxynitride (Silicon-rich SiO x N y ). Here, the oxygen-rich silicon oxynitride refers to the atomic ratio of silicon to oxygen in the silicon oxynitride being less than 1, and the silicon-rich silicon oxynitride refers to the atomic ratio of silicon to oxygen in the silicon oxynitride being greater than 1.

[0099] In this way, the second sacrificial layer 22 has a higher hardness, and can improve the etching selectivity and have a more uniform etching effect. Meanwhile, the first sacrificial layer 21 is more easily etched, and can be etched and removed together with the etching by-product 12. The remaining first sacrificial layer 21 forms a first layer 31 with a larger critical dimension, so that the sidewall of the first layer 31 is recessed in the sidewall of the second layer 32. For example, the etching liquid of the wet etching includes a diluted hydrofluoric acid solution, which is used to etch and remove the etching by-product 12, and etch the sidewall of the first layer 31 to reduce the circumference of the first layer 31.

[0100] The second layer 32 covers the first layer 31 in the orthographic projection of the substrate 10, and the distance between the edge of the orthographic projection of the second layer 32 on the substrate 10 and the edge of the orthographic projection of the first layer 31 on the substrate 10 is less than 1.5 nm. In this way, the size of the first layer 31 is not too small, and the first layer 31 can support the second layer 32. The orthographic projection of the first layer 31 on the substrate 10 is located in the active region 11, and the distance between the edge of the orthographic projection of the first layer 31 on the substrate 10 and the edge of the active region 11 is also less than 1.5 nm.

[0101] Referring to Figure 12 In the case where the first sacrificial layer 21 includes an oxide and the second sacrificial layer 22 includes a nitride or an oxynitride, or the first sacrificial layer 21 includes an oxygen-rich silicon oxide compound and the second sacrificial layer 22 includes a silicon-rich silicon oxide compound, the boss 30 is removed, and each active region 11 is restored to a vertical state from the tilted state. The method includes the following steps.

[0102] Step a: reacting the second layer 32 and the first layer 31 with a reaction gas to form a reaction product 40 on the surface of the first layer 31 and the second layer 32;

[0103] Step b: heating the reaction product 40 to decompose the reaction product 40 into a plurality of gaseous products;

[0104] Steps a and b are repeated in sequence until the first layer 31 and the second layer 32 are both removed by reaction, and the active region 11 is restored to a vertical state from the tilted state.

[0105] The first layer 31 is formed by the first sacrificial layer 21, and the second layer 32 is formed by the second sacrificial layer 22. The first layer 31 includes an oxide, and the second layer 32 includes a nitride or an oxynitride. Alternatively, the first layer 31 includes an oxygen-rich silicon oxide compound, and the second layer 32 includes a silicon-rich silicon oxide compound.

[0106] The first layer 31 and the second layer 32 can be etched by cyclic evaporation, i.e., the first layer 31 and the second layer 32 are divided into a plurality of parts, and are removed by reaction multiple times. Specifically, as shown in FIG. 6, the first layer 31 and the second layer 32 are divided into a plurality of parts 31a, 31b, 32a, and 32b, and are removed by reaction multiple times. Figure 12As shown, the reaction gas reacts with the first layer 31 and the second layer 32 to form a reaction product 40, the reaction product 40 is located on the surface of the first layer 31 and the second layer 32, and the reaction product 40 is heated to decompose and form a plurality of gas products, thereby exposing the remaining first layer 31 and second layer 32, and repeating the process of generating the reaction product 40 and decomposing the reaction product 40 until all the first layer 31 and the second layer 32 are completely removed.

[0107] The first temperature at which the reaction gas reacts with the second layer 32 and the first layer 31 to form the reaction product 40 is less than the second temperature at which the reaction product 40 decomposes, and the semiconductor structure is in a cycle of the first temperature and the second temperature until the first layer 31 and the second layer 32 are completely removed. The reaction of the reaction gas with the second layer 32 and the reaction of the reaction gas with the first layer 31 is not a combination reaction, and in addition to the reaction product 40, other products are all gases.

[0108] In some examples, the material of the first layer 31 includes silicon oxide, and the material of the second layer 32 includes silicon nitride or silicon oxynitride; or the material of the first sacrificial layer 21 includes oxygen-rich silicon oxynitride, and the material of the second sacrificial layer 22 includes silicon-rich silicon oxynitride; the reaction gas includes ammonia and hydrofluoric acid gas, and the reaction product 40 is heated to 100-200°C. The reaction of silicon oxide, ammonia and hydrofluoric acid gas forms ammonium fluorosilicate and oxygen, the reaction of silicon nitride, ammonia and hydrofluoric acid gas forms ammonium fluorosilicate and nitrogen, and the chemical formula of ammonium fluorosilicate is (NH4)2SiF6. Ammonium fluorosilicate decomposes to form hydrogen, hydrofluoric acid gas and silicon tetrafluoride gas when heated.

[0109] In another possible implementation, the material of the first sacrificial layer 21 includes carbon, and the material of the second sacrificial layer 22 includes nitride or oxynitride, as shown in FIG. 6, and the reaction gas includes hydrogen and nitrogen. Figure 13 Before the wet etching to remove the etching byproduct 12, the method further includes: using a first etching gas to dry etch and remove part of the side wall of the first layer 31, so that the side wall of the first layer 31 is recessed in the side wall of the second layer 32, and part of the etching byproduct 12 is etched and removed.

[0110] The first etching gas etches the side wall of the first layer 31 to reduce the circumference of the first layer 31, and the side wall of the first layer 31 is recessed in the side wall of the second layer 32. The first etching gas includes hydrogen and nitrogen, and the first etching gas also etches and removes part of the etching byproduct 12, and the selectivity of the first etching gas to the first layer 31 is greater than the selectivity to the etching byproduct 12, and the etching byproduct 12 also needs to be removed by cleaning. In the process of etching the first layer 31 and the etching byproduct 12, dry etching is adopted, no liquid is generated, and no tilt is generated, and the second layer 32, the first layer 31 and the active region 11 remain straight.

[0111] The second layer 32 covers the first layer 31 in the projection of the substrate 10, and the edge of the projection of the second layer 32 on the substrate 10 is less than 1.5 nm from the edge of the projection of the first layer 31 on the substrate 10, so as to avoid the size of the first layer 31 being too small to support the second layer 32. The projection of the first layer 31 on the substrate 10 is located in the active region 11, and the edge of the projection of the first layer 31 on the substrate 10 is also less than 1.5 nm from the edge of the active region 11.

[0112] Referring to Figure 14 and Figure 15 In the example where the first sacrificial layer 21 includes carbon and the second sacrificial layer 22 includes nitride or oxynitride, the removal of the protrusions 30 exposes the active regions 11.

[0113] Step a: reacting the second layer 32 with a reaction gas to form a reaction product 40 on the surface of the second layer 32.

[0114] Step b: heating the reaction product 40 to decompose the reaction product 40 into multiple gas products.

[0115] Steps a and b are repeated in sequence until the second layer 32 is removed by reaction and the first layer 31 is exposed, and the active regions 11 are released from the tilted state.

[0116] The first layer 31 is removed by dry etching with a second etching gas, and the active regions 11 are exposed.

[0117] The first layer 31 is formed by the first sacrificial layer 21, and the second layer 32 is formed by the second sacrificial layer 22. The first layer 31 includes carbon, and the second layer 32 includes nitride or oxynitride. The second layer 32 can be removed by cyclic evaporation etching, and the first layer 31 is removed by dry etching, such as ashing.

[0118] As shown in Figure 14 The reaction gas reacts with the second layer 32 to form a reaction product 40 on the surface of the second layer 32, and the reaction product 40 is heated to decompose the reaction product 40 into multiple gas products, thereby exposing the remaining second layer 32. The process of generating the reaction product 40 and decomposing the reaction product 40 is repeated until all of the second layer 32 is completely removed and the first layer 31 is exposed.

[0119] The first temperature at which the reaction gas reacts with the second layer 32 to form the reactant 40 is less than the second temperature at which the reactant 40 decomposes, and the semiconductor structure is in a cycle of the first temperature and the second temperature until the first layer 31 is removed by reaction. The reaction between the reaction gas and the second layer 32 is not a combination reaction, and other products are all gases except the reactant 40.

[0120] When the second layer 32 is removed by reaction, the active region 11 is no longer tilted and returns to a vertical state because the second layer 32 is in contact and adheres. As shown in FIG. 4, the first layer 31 is also connected to the active region 11, and the first layer 31 is removed by dry etching to expose the active region 11. The second etching gas includes hydrogen or helium, which avoids loss of the critical dimension of the active region 11 while removing the first layer 31. Figure 15

[0121] For example, the material of the second layer 32 includes silicon nitride or silicon oxynitride, the reaction gas includes ammonia and hydrofluoric acid gas, and the reactant 40 is heated to 100-200°C. Silicon oxide, ammonia, and hydrofluoric acid gas react to form ammonium fluorosilicate and oxygen, silicon nitride, ammonia, and hydrofluoric acid gas react to form ammonium fluorosilicate and nitrogen, and the chemical formula of ammonium fluorosilicate is (NH4)2SiF6. Ammonium fluorosilicate decomposes into hydrogen, hydrofluoric acid gas, and silicon tetrafluoride gas when heated.

[0122] In the description of the embodiments or implementations, each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be mutually referred to. The description of the terms "one implementation", "some implementations", "exemplary implementation", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the implementation or example are included in at least one implementation or example of the disclosure. In the description, the exemplary description of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more implementations or examples as appropriate.

[0123] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the disclosure, but not to limit them; although the disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the disclosure.​

Claims

1. A method for fabricating a semiconductor structure, characterized in that, include: A sacrificial structure is formed on the substrate; The sacrificial structure and the substrate are etched, and a plurality of spaced active regions are formed in the substrate, with etching byproducts between adjacent active regions. The sacrificial structure forms protrusions corresponding to each active region. Wet etching removes the etching byproducts, and the adjacent protrusions contact and adhere to each other in a portion of their area away from the substrate. The active regions connected to each protrusion are spaced apart and in an inclined state. Remove the protrusion, and each active area will be released from its tilted state and restored to an upright position.

2. The manufacturing method according to claim 1, characterized in that, Forming the sacrificial structure on the substrate includes: forming at least two sacrificial layers stacked sequentially on the substrate, wherein the at least two sacrificial layers form the sacrificial structure; Etching the sacrificial structure and the substrate includes: etching each of the sacrificial layers and the substrate to form the active region and the protrusion, wherein the protrusion includes at least two layers, and the number of the layers is less than or equal to the number of the sacrificial layers, and each layer corresponds to one sacrificial layer.

3. The manufacturing method according to claim 2, characterized in that, Forming the sacrificial structure on the substrate includes: A first sacrificial layer is formed on the substrate, a second sacrificial layer is formed on the first sacrificial layer, and a third sacrificial layer is formed on the second sacrificial layer, wherein the third sacrificial layer, the second sacrificial layer, and the first sacrificial layer form the sacrificial structure; Etching the sacrificial structure and the substrate includes: The third sacrificial layer, a portion of the second sacrificial layer, a portion of the first sacrificial layer, and a portion of the substrate are etched away to form the active region and the protrusion, wherein the protrusion includes a first layer and a second layer, the first layer includes the remaining first sacrificial layer, and the second layer includes the remaining second sacrificial layer.

4. The manufacturing method according to claim 3, characterized in that, Etching removes the third sacrificial layer, a portion of the second sacrificial layer, a portion of the first sacrificial layer, and a portion of the substrate, including: The third sacrificial layer is etched to form a preset pattern; Using the third sacrificial layer as a mask, the second sacrificial layer, the first sacrificial layer, and the substrate are etched, and the third sacrificial layer is removed during the etching of the second sacrificial layer, the first sacrificial layer, and the substrate to form the protrusion and the active region.

5. The manufacturing method according to claim 4, characterized in that, The material of the third sacrificial layer includes polycrystalline silicon, and the material of the substrate includes silicon.

6. The manufacturing method according to claim 3, characterized in that, Wet etching removes the etching byproducts, including: Wet etching removes the etching byproducts. The second layer, the first layer, and the active region are tilted under the action of capillary force. Adjacent second layers are in contact and adhere to each other. Each first layer is spaced apart, and each active region is spaced apart.

7. The manufacturing method according to claim 6, characterized in that, The first sacrificial layer is made of an oxide, and the second sacrificial layer is made of a nitride or a nitrogen oxide; or, the first sacrificial layer is made of an oxygen-rich silicon oxide compound, and the second sacrificial layer is made of a silicon-rich silicon oxide compound. While wet etching removes the etching byproducts, it also etches away part of the sidewalls of the first layer, causing the sidewalls of the first layer to be recessed into the sidewalls of the second layer.

8. The manufacturing method according to claim 7, characterized in that, The etching solution used in the wet etching process includes a diluted hydrofluoric acid solution.

9. The manufacturing method according to claim 6 or 7, characterized in that, Removing the protrusion and restoring each active region to its upright position after the tilting state is lifted includes: Step a: React the reactant gas with the second layer and the first layer to form reactants on the surfaces of the first layer and the second layer; Step b: Heating the reactants causes them to decompose and form various gaseous products; Steps a and b are repeated sequentially until both the first layer and the second layer are removed by the reaction, and the active region is released from the tilt state and exposed.

10. The manufacturing method according to claim 9, characterized in that, The material of the first layer includes silicon oxide, and the material of the second layer includes silicon nitride or silicon oxynitride; or, the material of the first sacrificial layer includes oxygen-rich silicon oxynitride, and the material of the second sacrificial layer includes silicon-rich silicon oxynitride. The reaction gases include ammonia and hydrofluoric acid, and the reactants are heated to 100°C-200°C.

11. The manufacturing method according to claim 6, characterized in that, The first sacrificial layer is made of carbon, and the second sacrificial layer is made of nitride or nitrogen oxide. Before wet etching to remove the etching byproducts, the process further includes: using a first etching gas to dry-etch away a portion of the sidewalls of the first layer, causing the sidewalls of the first layer to be recessed into the sidewalls of the second layer, and etching away a portion of the byproducts.

12. The manufacturing method according to claim 11, characterized in that, Removing the protrusion and restoring each active region to its upright position after the tilting state is lifted includes: Step a: React the reactant gas with the second layer to form reactants on the surface of the second layer; Step b: Heating the reactants causes them to decompose and form various gaseous products; Steps a and b are repeated sequentially until the second layer is removed by the reaction, the first layer is exposed, and the active region is released from the tilted state. The first layer is removed by dry etching with a second etching gas, exposing the active region.

13. The manufacturing method according to claim 12, characterized in that, The first etching gas includes hydrogen and nitrogen, and the second etching gas includes hydrogen or helium.

14. The manufacturing method according to claim 12 or 13, characterized in that, The material of the second layer includes silicon nitride or silicon oxynitride, the reaction gas includes ammonia and hydrofluoric acid, and the reactants are heated to 100°C-200°C.

15. The manufacturing method according to claim 7 or 11, characterized in that, The orthographic projection of the second layer on the substrate covers the orthographic projection of the first layer on the substrate, and the distance between the edge of the orthographic projection of the second layer on the substrate and the edge of the orthographic projection of the first layer on the substrate is less than 1.5 nm.

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