A method for removing polysilicon gates in a semiconductor process

Abstract

This invention discloses a method for removing polysilicon gates in semiconductor processes, comprising an etchant spraying stage. The etchant spraying stage involves spraying a first solvent and a second solvent onto the wafer surface. The first solvent is sprayed continuously, while the second solvent is sprayed intermittently. During the spraying process, the second solvent mixes with the first solvent. The mixture of the first and second solvents is used to etch the (111) interface of the polysilicon gate, and the first solvent is used to etch the non-(111) interface of the polysilicon. This invention achieves complete removal of polysilicon without residue by continuously spraying the first solvent and intermittently spraying the second solvent. Compared to existing etching methods that require cleaning and drying after each use of ammonia solution, this method simplifies the process flow by etching polysilicon continuously, resulting in higher efficiency in removing polysilicon residue and less consumption of surrounding film.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device fabrication technology, and more specifically to a method for removing polysilicon gates in semiconductor processes. Background Technology

[0002] In semiconductor fabrication processes, the removal of polysilicon gates is necessary when fabricating the back gate structure of fin field-effect transistors or semiconductor nanowire devices. However, residues often remain during this process, preventing complete removal. This is because when using chemical solvents as etchants to etch polysilicon, the (111) interface is often not effectively etched, resulting in polysilicon residues that affect the subsequent pattern fabrication and yield.

[0003] To solve the above problems, the current common practice is to use a step-by-step etching method. For example, in the first step, hydrofluoric acid is used to remove the oxides on the surface of polysilicon. In the second step, two solutions are used to etch polysilicon. The polysilicon (111) interface is etched with a mixture of two or more solutions, and then one of the solutions is used to etch the other interfaces of polysilicon. The polysilicon (111) interface is etched with the mixture, and then the other interfaces are etched with one solution. In this way, the etching of the polysilicon (111) surface and other surfaces is carried out alternately in the second step. In addition, after each etching is completed in the second step, cleaning and drying are performed.

[0004] With the development of semiconductor technology, the integration level of semiconductor devices has been gradually increased in order to meet the demand for miniaturization. The increase in integration level requires a reduction in the size of contact holes in semiconductor devices. However, smaller contact holes have a larger aspect ratio, which means that during the etching process, the chemical solution is increasingly unable to reach the (111) surface of polysilicon, resulting in residues. The existing methods described above cannot meet the demand for miniaturization of semiconductor devices. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing solutions for removing polysilicon gates cannot reach the (111) surface of polysilicon as the aspect ratio increases, resulting in residues. The purpose is to provide a method for removing polysilicon gates in semiconductor processes to solve the above problems.

[0006] This invention is achieved through the following technical solution:

[0007] A method for removing a polysilicon gate in a semiconductor process includes an etchant spraying stage, wherein the etchant spraying stage involves spraying a first solvent and a second solvent onto a wafer surface, wherein the spraying of the first solvent is continuous and the spraying of the second solvent is intermittent, and the second solvent mixes with the first solvent during the spraying process, wherein the mixture of the first solvent and the second solvent is used to etch the (111) interface of the polysilicon gate, and the first solvent is used to etch the non-(111) interface of the polysilicon.

[0008] Optionally, the first solvent is an aqueous ammonia solution, and the second solvent is a hydrogen peroxide solution.

[0009] Optionally, the time interval between two consecutive sprays of the second solvent is equal.

[0010] Optionally, the first solvent and the second solvent are sprayed using a first high-pressure nozzle and a second high-pressure nozzle, respectively, and the volume of solution sprayed by the first high-pressure nozzle and the second high-pressure nozzle is equal per unit time;

[0011] The first high-pressure nozzle and the second high-pressure nozzle are respectively connected to the first solvent container and the second solvent container.

[0012] Optionally, the system also includes a cleaning stage and a drying stage, both of which are performed after the etchant spraying stage is completed.

[0013] Optionally, the process also includes a stage for removing oxides from the polysilicon gate surface, which is performed before the etchant spraying stage, using hydrofluoric acid solution as the removal agent.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0015] The present invention provides a method for removing polysilicon gates in semiconductor processes, which completely removes polysilicon without residue by continuously spraying a first solvent and intermittently spraying a second solvent.

[0016] Compared to existing etching methods that require cleaning and drying after each use of ammonia solution, this method etches polysilicon in a continuous manner, greatly simplifying the process, improving the efficiency of removing polysilicon residues, and reducing the consumption of surrounding film. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0018] Figure 1 This is a schematic diagram of the etchant spraying stage in a method for removing polysilicon gates in a semiconductor process, provided by an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0020] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0021] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] With the development of semiconductor technology, the integration level of semiconductor devices has been gradually increased to meet the demand for miniaturization. This increased integration level requires reducing the size of contact holes in semiconductor devices. Smaller contact holes have a larger aspect ratio, which means that during etching, the chemical solution becomes increasingly unable to reach the (111) face of the polysilicon, leading to residue.

[0023] To address the above problems, this invention proposes a method for removing polysilicon gates in semiconductor processes. The specific solution is as follows:

[0024] Image attached Figure 1 As shown in the figure (wafer represents a wafer, chemical nozzle represents a solvent nozzle), in one embodiment, a method for removing polysilicon gates in a semiconductor process includes an etchant spraying stage, wherein the etchant spraying stage involves spraying a first solvent and a second solvent onto the wafer surface, wherein the first solvent is sprayed continuously, the second solvent is sprayed intermittently, and the second solvent mixes with the first solvent during the spraying process, the mixture of the first solvent and the second solvent is used to etch the (111) interface of the polysilicon gate, and the first solvent is used to etch the non-(111) interface of the polysilicon.

[0025] Specifically, the first solvent, acting as an etchant, can etch the non-(111) interface of polysilicon, while the mixture of the first and second solvents can etch the (111) interface of polysilicon. During the etching process, both the first and second solutions are sprayed onto the wafer surface. The first solution is sprayed continuously, while the second solution is sprayed intermittently. When only the first solution is sprayed, the non-(111) interface of polysilicon is etched; when the second solution is also sprayed, the (111) interface of polysilicon is etched. The first and second solutions are mixed during the spraying process and simultaneously sprayed onto the wafer surface. This process of continuous spraying of the first solution and intermittent spraying of the second solution is repeated cyclically.

[0026] By continuously spraying the first solvent and intermittently spraying the second solvent, the polycrystalline silicon is completely removed without any residue.

[0027] In one embodiment, the first solvent is an aqueous ammonia solution, and the second solvent is a hydrogen peroxide solution. Furthermore, the time interval between two consecutive sprays of hydrogen peroxide solution is equal.

[0028] It also includes a cleaning stage and a drying stage, both of which are carried out after the etching agent spraying stage is completed.

[0029] The existing method for etching polysilicon gates, taking ammonia solution and hydrogen peroxide solution as an example, involves the following steps: First, hydrofluoric acid is used to remove oxides from the surface of the polysilicon; second, a mixture of ammonia solution and hydrogen peroxide solution is used to etch the polysilicon (111) interface, followed by cleaning and drying; then, ammonia solution is used to etch other interfaces of the polysilicon, followed by cleaning and drying; then, a mixture of ammonia solution and hydrogen peroxide is used to etch the polysilicon (111) interface, followed by cleaning and drying; then, ammonia solution is used to etch other interfaces, followed by cleaning and drying.

[0030] Compared to existing etching methods that require cleaning and drying after each use of ammonia solution, this method etches polysilicon in a continuous manner, greatly simplifying the process, improving the efficiency of removing polysilicon residues, and reducing the consumption of surrounding film.

[0031] In another embodiment, the ammonia solution and the hydrogen peroxide solution are sprayed using a first high-pressure nozzle and a second high-pressure nozzle, respectively, and the volume of solution sprayed by the first high-pressure nozzle and the second high-pressure nozzle is equal per unit time; the first high-pressure nozzle and the second high-pressure nozzle are respectively connected to a first solvent container and a second solvent container.

[0032] It also includes a stage for removing oxides from the polysilicon gate surface. This stage is performed before the etchant spraying stage and uses hydrofluoric acid solution as the removal agent.

[0033] All processes, methods, and devices not mentioned in the embodiments of this invention are known technologies and will not be described in detail here.

[0034] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for removing polysilicon gates in semiconductor processes, characterized in that, The process includes an etchant spraying stage, wherein the etchant spraying stage involves spraying a first solvent and a second solvent onto the wafer surface. The first solvent is sprayed continuously, while the second solvent is sprayed intermittently. During the spraying process, the second solvent mixes with the first solvent. The mixture of the first solvent and the second solvent is used to etch the (111) interface of the polysilicon gate, and the first solvent is used to etch the non-(111) interface of the polysilicon. The first solvent is an aqueous ammonia solution, and the second solvent is a hydrogen peroxide solution; The time interval between two consecutive sprays of the second solvent is equal.

2. The method for removing polysilicon gates in semiconductor processes according to claim 1, characterized in that, The first solvent and the second solvent are sprayed using a first high-pressure nozzle and a second high-pressure nozzle, respectively, and the volume of solution sprayed by the first high-pressure nozzle and the second high-pressure nozzle is equal per unit time; The first high-pressure nozzle and the second high-pressure nozzle are respectively connected to the first solvent container and the second solvent container.

3. The method for removing polysilicon gates in a semiconductor process according to claim 1, characterized in that, It also includes a cleaning stage and a drying stage, both of which are performed after the etching agent spraying stage is completed.

4. The method for removing polysilicon gates in a semiconductor process according to claim 1, characterized in that, It also includes a stage for removing oxides from the polysilicon gate surface, which is performed before the etchant spraying stage, using hydrofluoric acid solution as the removal agent.

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