Method for etching a trench

Abstract

The application provides a channel etching method, which comprises the following steps: providing an object to be etched, which comprises a plurality of fin structures, each of which comprises a sacrificial layer and a channel layer which overlap with each other, and the widths of the plurality of fin structures along a channel direction are different; after one etching of the object to be etched, cyclically performing surface treatment, blowing treatment and secondary etching until the sacrificial layers of all the fin structures are etched; the blowing treatment is used for removing a first substance and a second substance; the first substance represents a substance introduced during the surface treatment; the second substance represents a substance generated during the surface treatment; the technical scheme realizes high selective ratio etching of SiGe relative to Si, solves the problem of low selective ratio of the sacrificial layer relative to a dielectric material (such as SiN) caused by the surface treatment process, and further reduces the damage of the dielectric material (such as SiN) caused by a subsequent etching process.

Description

Technical Field

[0001] This invention relates to the field of semiconductor devices, and more particularly to a method for etching channels. Background Technology

[0002] The multi-step etching process proposed in patent CN114639606A involves oxidation treatment to improve the etching selectivity of SiGe relative to Si. However, oxidation treatment reduces the etching selectivity of SiGe relative to the dielectric material. This increases the etching rate of the dielectric material (such as SiN), thus affecting device performance. Therefore, identifying the reasons for the reduced etching selectivity of SiGe relative to the dielectric material, and developing a channel etching process to avoid the problem of reduced SiGe / Si selectivity caused by oxidation treatment, has become a key technical focus for those skilled in the art. Summary of the Invention

[0003] This invention provides a channel etching method to address the problem that the sacrificial layer is relatively low relative to the dielectric material (such as SiN) due to the surface treatment process, thereby reducing the damage to the dielectric material (such as SiN) caused by subsequent etching processes.

[0004] According to a first aspect of the present invention, a method for etching a channel is provided, comprising:

[0005] An object to be etched is provided, the object to be etched includes a plurality of fin structures formed on a substrate, each fin structure including an overlapping sacrificial layer and a channel layer, the plurality of fin structures having different widths along the channel direction;

[0006] After etching the object to be etched once, the first process is repeated multiple times until all the sacrificial layers of the fin structure are etched away; wherein, the first process includes sequential surface treatment purging and secondary etching.

[0007] Both the first etching and the second etching each include multiple etching steps;

[0008] The purging process is used to remove a first substance and a second substance; the first substance is a substance introduced during the surface treatment; the second substance is a substance generated during the surface treatment.

[0009] The first etching is used to etch away all the sacrificial layers of the fin structure with the smallest current width among the plurality of fin structures, as well as part of the sacrificial layers of other fin structures with wider widths.

[0010] The surface treatment is used to form a protective layer on the exposed surfaces of the channel layer and the remaining sacrificial layer of the object to be etched;

[0011] The secondary etching is used to etch away all the sacrificial layers of the fin structure with the second widest width, as well as part of the sacrificial layers of other fin structures with the larger current width, and the protective layer.

[0012] Optionally, the purging process includes a first purging process and a second purging process;

[0013] The first purging process is used to remove a first substance from the reaction chamber; the second purging process is used to remove a second substance from the reaction chamber and / or the surface of the object to be etched.

[0014] The flow rate and purging time of the purging gas during the second purging process are greater than those of the purging gas during the first purging process.

[0015] Optionally, when performing the second purging process, the flow rate of the purging gas is greater than 1000 sccm.

[0016] Optionally, when performing the second purging process, the purging time is greater than or equal to 120 seconds.

[0017] Optionally, the etching of the object to be etched and the surface treatment are performed in the same reaction chamber.

[0018] Optionally, the first purging process and / or the second purging process may be performed using an inert gas.

[0019] Optionally, the surface treatment is an oxidation treatment, and the protective layer is an oxide layer.

[0020] Optionally, the first substance is an oxygen-containing substance.

[0021] Optionally, when performing the first purging process, the flow rate of the purging gas is 300-500 sccm.

[0022] Optionally, the purging time during the first purging process is 40s-60s.

[0023] Optionally, after performing the first purging process and / or the second purging process, the method further includes: evacuating the reaction chamber.

[0024] Optionally, the number of fin structures is two, specifically a first fin structure formed in a first region on the substrate and a second fin structure formed in a second region on the substrate; the first fin structure includes an overlapping first sacrificial layer and a first channel layer, and the second fin structure includes an overlapping second sacrificial layer and a second channel layer; the width of the first sacrificial layer and the first channel layer along the channel direction is smaller than the width of the second sacrificial layer and the second channel layer along the channel direction;

[0025] The object to be etched is etched once to remove all of the first sacrificial layer and part of the second sacrificial layer;

[0026] An oxide layer is formed on the exposed surfaces of the remaining sacrificial layer and channel layer of the object to be etched;

[0027] The first purging process is performed to remove the first substance from the reaction chamber; the first substance is a substance introduced during the formation of the oxide layer.

[0028] A second purging process is performed to remove a second substance from the reaction chamber and / or the surface of the object to be etched; the second substance characterizes the substance produced during the formation of the oxide layer;

[0029] The object to be etched is subjected to a second etching process to remove all the sacrificial layer and the oxide layer on the second region.

[0030] Optionally, the channel layer is made of Si, and the sacrificial layer is made of SiGe.

[0031] According to a second aspect of the present invention, a method for fabricating a semiconductor device is provided, comprising: an etching method for a channel as described in any one of the first aspects of the present invention.

[0032] According to a third aspect of the present invention, a method for manufacturing an electronic device is provided, comprising the method for preparing a semiconductor device as described in the second aspect of the present invention.

[0033] The present invention provides a channel etching method that removes the first and second substances remaining on the surface of the object to be etched and in the reaction chamber during the surface treatment process by cyclically purging. This ensures a high selectivity etching ratio of SiGe relative to the dielectric material (such as SiN), guarantees the etching selectivity of the channel release process for the dielectric material, and reduces the damage to the dielectric material (such as SiN) by subsequent etching processes, thereby improving device performance. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic flowchart of a trench etching method provided in one embodiment of the present invention;

[0036] Figure 2 This is a schematic flowchart of a channel etching method provided in a specific embodiment of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] The multi-step etching process proposed in patent CN114639606A involves oxidation treatment to improve the etching selectivity of SiGe relative to Si. However, the inventors of this application discovered during further experiments that the introduction of oxidation treatment causes significant damage to the dielectric material (such as SiN) in subsequent etching processes, thereby affecting device performance.

[0040] The inventors of this application also discovered through repeated experiments that when a high-flux of Ar or N2 is circulated and purged into the reaction chamber for a certain period of time after oxidation treatment, the damage to the dielectric material (such as SiN) in the subsequent etching process is restored to the level before the oxidation treatment was introduced.

[0041] The inventors discovered through research that this phenomenon is due to residual oxygen on the surface of the object to be etched and the cavity surface after oxidation treatment. This residual oxygen participates in subsequent etching reactions, leading to a decrease in the etching selectivity of SiGe relative to the dielectric material. Therefore, it increases the etching rate of the dielectric material (such as SiN), thereby affecting device performance.

[0042] Meanwhile, numerous studies have shown that when dry etching SiN (containing N dielectric) using F-based gases, introducing oxygen into the etching gas significantly increases the etching rate of SiN. This is because introducing oxygen into the etching process leads to the generation of NO in the etching gas composition. NO reacts with the FN bonds on the SiN surface to generate NO2, releasing F atoms. This, in turn, accelerates the migration of F atoms from the FN bond into the SiN interior, thereby accelerating the SiN etching rate.

[0043] In view of this, the inventors of this application propose that by using a cyclic purging process (introducing inert gases such as Ar or N2 for a long time or at high flow rate), the residual oxygen on the surface of the object to be etched and the surface of the reaction chamber during the oxidation process is completely removed, thereby achieving a high selectivity etching ratio of SiGe relative to dielectric materials (such as SiN), ensuring the etching selectivity of the channel release process for the dielectric material, and thus reducing the damage to the dielectric material (such as SiN) by subsequent etching processes, thereby improving device performance.

[0044] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0045] According to an embodiment of the present invention, a method for etching a channel is provided, comprising:

[0046] S11: Provide an object to be etched, the object to be etched includes a plurality of fin structures formed on a substrate, each fin structure includes overlapping sacrificial layers and channel layers, and the width of the plurality of fin structures along the channel direction is different.

[0047] S12: After etching the object to be etched once, the first process is repeated multiple times until all the sacrificial layers of the fin structure are etched away; wherein, the first process includes sequential surface treatment purging and secondary etching.

[0048] Both the first etching and the second etching each include multiple etching steps;

[0049] The purging process is used to remove the first substance and the second substance; the first substance is characterized by the substance introduced during the surface treatment; the second substance is characterized by the substance generated during the surface treatment; specifically, the secondary etching is a dry etching method based on F-based gases (NF3, CF4).

[0050] The first etching is used to etch away all the sacrificial layers of the fin structure with the smallest current width among the plurality of fin structures, as well as part of the sacrificial layers of other fin structures with wider widths.

[0051] The surface treatment is used to form a protective layer on the exposed surfaces of the channel layer and the remaining sacrificial layer of the object to be etched;

[0052] The secondary etching is used to etch away all the sacrificial layers of the second widest fin structure after the previous etching, as well as parts of the sacrificial layers of other fin structures with larger current widths, and the protective layer. The other fin structures with larger current widths become the fin structures with the smallest current width in the next etching, and so on, until the sacrificial layers of all fin structures have been etched away.

[0053] The technical solution provided by this invention not only creatively discovers the reason for the relatively low selectivity of SiGe relative to dielectric materials (such as SiN), but also further removes the first and second substances remaining on the surface of the object to be etched and in the reaction chamber during the surface treatment process by cyclically purging, thereby ensuring a high selectivity etching ratio of SiGe relative to dielectric materials (such as SiN), ensuring the etching selectivity of the channel release process for the dielectric material, and thus reducing the damage to the dielectric material (such as SiN) by subsequent etching processes, thereby improving device performance.

[0054] In one embodiment, the purging process includes a first purging process and a second purging process;

[0055] The first purging process is used to remove a first substance from the reaction chamber; the second purging process is used to remove a second substance from the reaction chamber and / or the surface of the object to be etched.

[0056] The flow rate and purging time of the purging gas during the second purging process are greater than those of the purging gas during the first purging process.

[0057] The object to be etched further includes inner sidewalls formed at both ends of the sacrificial layer along the horizontal direction; the inner sidewalls are made of a dielectric material (such as SiN). Because a first substance and a second substance are introduced during the surface treatment of the object to be etched, the selectivity of the sacrificial layer (SiGe) relative to the dielectric material (such as SiN, SiON, SiCON, SiCO, SiCN, etc.) decreases; therefore, when the sacrificial layer is etched to release the channel layer, the etching rate of the inner sidewalls (made of dielectric material) increases, resulting in the loss of the inner sidewalls. When the first and second purging processes are combined in a cyclical manner, the first and second substances remaining on the surface of the object to be etched and in the reaction chamber during the surface treatment process are removed, thereby ensuring the etching selectivity of the channel release process for the dielectric material.

[0058] In one embodiment, after performing the first purging process and the second purging process in step S12, the method further includes: evacuating the reaction chamber.

[0059] To facilitate industrial production, in a preferred embodiment, the etching of the object to be etched and the surface treatment are performed in the same reaction chamber.

[0060] In another embodiment, etching and surface treatment of the object to be etched are performed in two different chambers.

[0061] In one embodiment, the flow rate of the purging gas is greater than 1000 sccm when performing the second purging process.

[0062] In one embodiment, the purging time varies depending on the process when performing the second purging treatment, and the total purging time is greater than or equal to 120 seconds.

[0063] In one embodiment, the flow rate of the purging gas is 300-500 sccm during the first purging process.

[0064] In one embodiment, the purging time during the first purging process is 40s-60s.

[0065] In one embodiment, the purging gas used for the first purging process and / or the second purging process is an inert gas. Specifically, the purging gas can be nitrogen, argon, or other inert gases.

[0066] In one embodiment, the surface treatment is an oxidation treatment, and the protective layer is an oxide layer.

[0067] In one embodiment, the first substance is oxygen or an oxygen free radical.

[0068] In one embodiment, the number of fin structures is two, specifically a first fin structure formed in a first region on the substrate and a second fin structure formed in a second region on the substrate; the first fin structure includes an overlapping first sacrificial layer and a first channel layer, and the second fin structure includes an overlapping second sacrificial layer and a second channel layer; the width of the first sacrificial layer and the first channel layer along the channel direction is smaller than the width of the second sacrificial layer and the second channel layer along the channel direction; specifically, the channel layer is made of Si, and the sacrificial layer is made of SiGe.

[0069] S121: Perform an etching operation on the object to be etched to etch away all of the first sacrificial layer and part of the second sacrificial layer;

[0070] S122: An oxide layer is formed on the exposed surfaces of the remaining sacrificial layer and channel layer of the object to be etched;

[0071] S123: Perform the first purging process to remove the first substance from the reaction chamber; the first substance is a substance introduced during the formation of the oxide layer; the first substance is oxygen;

[0072] S124: Perform a second purging process to remove a second substance from the reaction chamber and / or the surface of the object to be etched; the second substance is a substance generated during the formation of the oxide layer; the second substance is an impurity generated by oxidation of the reaction chamber or the surface of the object to be etched; specifically, the second substance is: a residue of oxygen-containing substances (oxygen / oxygen free radicals / oxygen-containing functional groups).

[0073] S125: Perform a second etching on the object to be etched to etch away all the sacrificial layer and the oxide layer on the second region.

[0074] The technical solution provided by this invention removes residual oxygen and oxidation-generated substances from the surface of the object to be etched and the reaction chamber during the oxide layer formation process by combining a first purging process and a second purging process. This achieves high selectivity etching of SiGe / Si while ensuring high selectivity etching of the sacrificial layer material relative to the dielectric material (such as SiN). This, in turn, ensures the etching selectivity of the channel release process for the dielectric material, thereby reducing damage to the dielectric material (such as SiN) in subsequent etching processes and improving device performance.

[0075] Secondly, according to an embodiment of the present invention, a method for fabricating a semiconductor device is also provided, comprising: the etching method for the channel described in any of the foregoing embodiments of the present invention.

[0076] In addition, according to one embodiment of the present invention, a method for manufacturing an electronic device is also provided, including the method for preparing a semiconductor device as described in the foregoing embodiments of the present invention.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for etching channels, characterized in that, include: An object to be etched is provided, the object to be etched includes a plurality of fin structures formed on a substrate, each fin structure including an overlapping sacrificial layer and a channel layer, the plurality of fin structures having different widths along the channel direction; After etching the object to be etched once, the first process is repeated multiple times until all the sacrificial layers of the fin structure are etched away; wherein, the first process includes sequential surface treatment purging and secondary etching. Both the first etching and the second etching each include multiple etching steps; The purging process is used to remove a first substance and a second substance; the first substance is a substance introduced during the surface treatment; the second substance is a substance generated during the surface treatment. The first etching is used to etch away all the sacrificial layers of the fin structure with the smallest current width among the plurality of fin structures, as well as part of the sacrificial layers of other fin structures with wider widths. The surface treatment is used to form a protective layer on the exposed surfaces of the channel layer and the remaining sacrificial layer of the object to be etched; The secondary etching is used to etch away all the sacrificial layers of the fin structure with the second widest width, as well as part of the sacrificial layers of other fin structures with the larger current width, and the protective layer.

2. The etching method for the trench according to claim 1, characterized in that, The purging process includes a first purging process and a second purging process; The first purging process is used to remove a first substance from the reaction chamber; the second purging process is used to remove a second substance from the reaction chamber and / or the surface of the object to be etched. In this process, the flow rate and purging time of the purging gas during the second purging process are greater than those of the purging gas during the first purging process.

3. The etching method for the trench according to claim 2, characterized in that, When performing the second purging process, the flow rate of the purging gas is greater than 1000 sccm.

4. The etching method for the trench according to claim 3, characterized in that, When performing the second purging process, the purging time is greater than or equal to 120 seconds.

5. The etching method for the trench according to claim 4, characterized in that, The etching and surface treatment of the object to be etched are carried out in the same reaction chamber.

6. The etching method for the trench according to claim 5, characterized in that, The first purging process and / or the second purging process are performed using an inert gas.

7. The etching method for the trench according to claim 6, characterized in that, The surface treatment is an oxidation treatment, and the protective layer is an oxide layer.

8. The etching method for the trench according to claim 7, characterized in that, The first substance is an oxygen-containing substance.

9. The etching method for the trench according to claim 8, characterized in that, During the first purging process, the flow rate of the purging gas is 300-500 sccm.

10. The etching method for the trench according to claim 9, characterized in that, When performing the first purging process, the purging time is 40s-60s.

11. The etching method for the channel according to claim 10, characterized in that, After performing the first purging process and the second purging process, the method further includes: The reaction chamber is evacuated.

12. The etching method for the channel according to claim 11, characterized in that, The number of fin structures is two, specifically a first fin structure formed in a first region on the substrate and a second fin structure formed in a second region on the substrate; the first fin structure includes an overlapping first sacrificial layer and a first channel layer, and the second fin structure includes an overlapping second sacrificial layer and a second channel layer; the width of the first sacrificial layer and the first channel layer along the channel direction is smaller than the width of the second sacrificial layer and the second channel layer along the channel direction. The object to be etched is etched once to remove all of the first sacrificial layer and part of the second sacrificial layer; An oxide layer is formed on the exposed surfaces of the remaining sacrificial layer and channel layer of the object to be etched; Perform the first purging process; Used to remove the first substance from the reaction chamber; the first substance is characterized by the substance introduced during the formation of the oxide layer; Perform a second purging treatment; A second substance used to remove the reaction chamber and / or the surface of the object to be etched; the second substance characterizes the substance produced during the formation of the oxide layer; The object to be etched is subjected to a second etching process to remove all the sacrificial layer and the oxide layer on the second region.

13. The etching method for the channel according to claim 12, characterized in that, The channel layer is made of Si, and the sacrificial layer is made of SiGe.

14. A method for fabricating a semiconductor device, characterized in that, include: The etching method for the channel according to any one of claims 1 to 13.

15. A method for manufacturing an electronic device, comprising the method for preparing the semiconductor device as described in claim 14.

Images