Cleaning method and forming method of AlScN thin film structure and semiconductor structure

Abstract

The invention provides a cleaning method and a forming method of an AlScN thin film structure and a semiconductor structure, and the cleaning method comprises the steps: providing a substrate, forming the AlScN thin film structure on the substrate, and completing a photoresist removing process on the substrate; and performing photoresist removal on the substrate by using a weakly alkaline or neutral cleaning solution, and then cleaning the substrate. According to the method, the weak alkaline or neutral cleaning solution, especially the RCA cleaning solution, is used for cleaning after photoresist removal, so that the AlScN surface is not damaged while by-products of dry etching and photoresist residues can be effectively removed, and the surface chap abnormity of the AlScN film is avoided; and the process compatibility is good, complicated means are not needed, the process adjustment is convenient, and the adjustment cost is low.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a cleaning method, a forming method of an AlScN thin film structure, and a semiconductor structure. Background Art

[0002] AlScN (aluminum scandium nitride) is a new type of piezoelectric material with excellent physical and electrical properties, and has important applications in many semiconductor technology fields. Taking microelectromechanical systems (MEMS) as an example, with the rapid development of MEMS technology, new piezoelectric materials such as AlScN are more and more widely used in MEMS sensors.

[0003] AlScN thin films can usually be prepared by thin film processes such as magnetron sputtering, molecular beam epitaxy (MBE), or metalorganic chemical vapor deposition (MOCVD). After the AlScN film layer is deposited, lithography and etching processes are used to form the required AlScN structure, which usually includes steps such as exposure, development, etching, and stripping. In order to carry out subsequent processes, after stripping, the possibly remaining photoresist or etching by-products also need to be cleaned and removed. This step usually uses EKC cleaning, and this EKC cleaning process often causes different degrees of cracking of the AlScN thin film, thereby affecting product performance.

[0004] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solutions of this application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art just because these solutions are described in the background art part of this application. Summary of the Invention

[0005] The purpose of the present invention is to provide a cleaning method, a forming method of an AlScN thin film structure, and a semiconductor structure to obtain an AlScN thin film structure with no abnormal cracking on the surface and no residues from the previous process.

[0006] To solve the above problems, in the first aspect, a cleaning method of an AlScN thin film structure is provided, including:

[0007] Providing a substrate on which an AlScN thin film structure is formed, and the substrate has completed the stripping process;

[0008] Using a weakly alkaline or neutral cleaning solution to perform post-stripping cleaning on the substrate.

[0009] Through research, it is found in this application that the abnormal cracking on the surface of AlScN is related to the reaction of a strongly alkaline cleaning solution in the Sc segregation region. Therefore, it is proposed to use a weakly alkaline or neutral cleaning solution to avoid this problem.

[0010] After the glue on the substrate is removed, the substrate is cleaned with an RCA cleaning solution. The RCA cleaning solution can effectively remove the by-products of dry etching and the residues of photoresist, and will not damage the AlScN surface.

[0011] Cleaning the substrate with an RCA cleaning solution after removing the glue includes: first cleaning the substrate with an SC-1 solution at a cleaning temperature of 70–80°C; rinsing the substrate with deionized water; and second cleaning the substrate with an SC-2 solution at a cleaning temperature of 70–80°C. This cleaning process has good compatibility with the existing technology, and is beneficial for removing the residues of the previous process, and will not damage the AlScN surface.

[0012] The SC-1 solution is a mixed solution of deionized water, hydrogen peroxide and ammonia water, and the volume ratio of deionized water: hydrogen peroxide: ammonia water is 5:1:1.

[0013] The SC-2 solution is a mixed solution of deionized water, hydrogen peroxide and hydrochloric acid, and the volume ratio of deionized water: hydrogen peroxide: hydrochloric acid is 6:1:1.

[0014] In a second aspect, the present application provides a method for forming an AlScN thin film structure, including:

[0015] Providing a substrate, and depositing an AlScN layer on the substrate;

[0016] Performing patterning on the AlScN layer to form an AlScN thin film structure;

[0017] Performing post-degluing cleaning on the substrate according to the cleaning method described in any one of the first aspect.

[0018] The AlScN layer is formed by any one of magnetron sputtering, molecular beam epitaxy or metal organic chemical vapor deposition.

[0019] The patterning includes: forming a photoresist layer on the AlScN layer; performing exposure and development on the photoresist layer to form a photoresist mask; using the photoresist mask as an etching mask to etch the AlScN layer to form an AlScN thin film structure; and performing degluing treatment to remove the remaining photoresist.

[0020] The etching treatment is a plasma etching process or a wet etching process; the degluing treatment is an ashing process.

[0021] In another aspect, the present application further provides a semiconductor structure obtained according to the cleaning method described in any one of the first aspect or the forming method described in any one of the second aspect.

[0022] Compared with the prior art, the beneficial effects of the present invention mainly include the following: 1) It can effectively remove the by-products of dry etching and the photoresist residues while not damaging the surface of AlScN, avoiding abnormal surface cracking of the AlScN film; 2) It has good process compatibility, does not require complex means, is convenient for process adjustment, and has low adjustment cost. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a flowchart of a cleaning method for an AlScN thin film structure provided by the present invention.

[0025] Figure 2 It is a flowchart of a forming method for an AlScN thin film structure provided by the present invention. Detailed Description of the Embodiments

[0026] Regarding the foregoing and other technical contents, features, and effects of the present invention, they will be clearly presented in the following detailed description of a preferred embodiment in conjunction with the reference drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front, or back, etc., are only with reference to the directions of the attached drawings. Therefore, the directional terms used are for illustration and not for limiting the present invention.

[0027] The following will elaborate on the embodiments of the present application in conjunction with the drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present application, many technical details are proposed to help the reader better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0028] The steps in the following embodiments do not correspond one by one to the content of the invention.

[0029] AlScN (aluminum scandium nitride) has important applications in the field of semiconductor technology. In the prior art, an AlScN film layer is usually deposited on a film layer such as Si or SiO2, and then lithography, etching, and degluing are performed to form the required AlScN structure; after degluing, EKC cleaning is usually performed to remove the residues on the substrate surface. However, after the above process flow, abnormal surface cracking is likely to occur on the surface layer of the AlScN thin film structure.

[0030] Through long-term observation and experiments by the inventors, it was found that after the deposition of the AlScN film layer, and after photolithography, etching, and resist stripping, the surface of the AlScN thin film was normal. However, when EKC cleaning was performed, abnormal surface cracking occurred on the surface of the AlScN thin film structure, indicating that it might be caused by EKC cleaning.

[0031] In the prior art, since the problem of abnormal surface cracking cannot be directly solved, in order to avoid abnormal surface film layers, some would choose to skip EKC cleaning (i.e., not perform EKC cleaning). However, skipping EKC cleaning would cause the by-products after dry etching and the photoresist residues to be unable to be removed, thus affecting the product performance to varying degrees.

[0032] In order to clarify the cause of the abnormal surface cracking of the AlScN thin film, the inventors conducted in-depth research on this and finally found that the abnormal cracking was related to the uneven distribution of Sc (scandium) during the film deposition process. That is, during the deposition of AlScN, the doping of Sc would introduce chemical inhomogeneity, making the Sc-enriched regions be preferentially corroded by the EKC solution, forming the origin of microcracks, and ultimately leading to abnormal surface cracking.

[0033] Considering that the current deposition process cannot prevent the uneven distribution of Sc elements during deposition and achieve absolute uniformity, it is necessary to improve the existing cleaning process after resist stripping. Research shows that due to the strong alkalinity of the EKC cleaning solution, the Sc-enriched regions in the AlScN film layer may react chemically with the EKC cleaning solution preferentially. The reaction products (such as hydroxides) will damage the film layer structure, form the origin of microcracks, and then lead to surface looseness or local peeling, ultimately manifested as cracking. Therefore, this application proposes that a compatible cleaning solution should be selected and a weakly alkaline or neutral cleaning solution: RCA solution should be used for cleaning after resist stripping.

[0034] Example 1

[0035] As Figure 1 shown is a flowchart of a cleaning method for an AlScN thin film structure provided by an embodiment of the present invention. Referring to Figure 1 , the present invention provides a cleaning method for an AlScN thin film structure, and the method includes the following steps:

[0036] Step 1: Provide a substrate, on which an AlScN thin film structure is formed and a resist stripping process has been performed.

[0037] It can be understood that the substrate is a semiconductor substrate, usually a silicon substrate; in other embodiments, it can also be a germanium substrate, a silicon carbide substrate, or a SOI substrate, etc. An AlScN thin film structure is formed on the surface of the substrate. The formation process of the AlScN thin film structure generally includes: 1) depositing an AlScN film layer; 2) forming the AlScN thin film structure through photolithography and etching processes; 3) removing the photoresist through a photoresist stripping process.

[0038] Step 2: Perform RCA cleaning, including the following steps:

[0039] S201: Perform the first cleaning using an SC-1 solution;

[0040] It can be understood that first, the first cleaning is performed using an SC-1 solution, and the cleaning temperature is 70–80 °C; the main function of this step is: to remove organic contaminants (such as photoresist residues, grease), to remove particulate contaminants through oxidation and micro-etching, to form a hydrophilic surface, and to reduce secondary contamination. The specific cleaning principle is: NH4OH provides an alkaline environment, and H2O2 oxidizes contaminants and decomposes organic substances to effectively remove the by-products after dry etching and photoresist residues. Specifically, the formulation of the SC-1 solution is: deionized water (H2O): hydrogen peroxide (H2O2): ammonia water (NH4OH) = 5:1:1 (volume ratio).

[0041] S202: Perform deionized water rinsing;

[0042] After the first cleaning, first rinse with deionized water to remove the residual SC-1 solution, and then use SC-2 for the second cleaning to avoid direct mixing of NH4OH and HCl (which will produce toxic NH3 and Cl2 gases).

[0043] S203: Perform the second cleaning using an SC-2 solution;

[0044] It can be understood that immediately afterwards, the second cleaning is performed using an SC-2 solution, and the cleaning temperature is 70–80 °C; the main function of this step is: to remove metal ions (such as Fe, Cu, Al, etc.) and alkali metal contaminants and prevent metal from redepositing on the silicon wafer surface. The specific principle is that HCl reacts with metal ions to form soluble chlorides, and H2O2 enhances the oxidation ability. Specifically, the formulation of the SC-2 solution is: deionized water (H2O): hydrogen peroxide (H2O2): hydrochloric acid (HCl) = 6:1:1 (volume ratio).

[0045] In other embodiments, according to process requirements, the mixing ratios of the SC-1 solution and the SC-2 solution can also be adjusted or other reagents can be introduced (such as introducing diluted hydrofluoric acid DHF to remove the oxide layer).

[0046] Embodiment 2

[0047] As Figure 2 shown is a flowchart of a method for forming an AlScN thin film structure provided by an embodiment of the present invention. Referring to Figure 2 , the present invention provides a method for forming an AlScN thin film structure, including the following steps:

[0048] Step 1: Provide a substrate and deposit an AlScN layer on the substrate.

[0049] It can be understood that the substrate is a semiconductor substrate, usually a silicon substrate; in other embodiments, it can also be a germanium substrate, a silicon carbide substrate, or a SOI substrate, etc.

[0050] The deposition process of the AlScN layer can generally be carried out by magnetron sputtering, molecular beam epitaxy (MBE), or metalorganic chemical vapor deposition (MOCVD). According to different actual situations, the AlScN layer can be directly deposited on the surface of the substrate, or the AlScN film layer can be deposited after other structures (such as a silicon layer or a silicon dioxide layer) have been pre-formed on the surface of the substrate.

[0051] Step 2: Pattern the AlScN layer to form the desired AlScN thin film structure.

[0052] In this embodiment, the patterning of the AlScN layer is carried out by photolithography and etching processes. Specifically, first, a photoresist layer is spin-coated on the AlScN layer; the photoresist layer is exposed, developed, etc., to pattern the photoresist layer to form a photoresist mask; using the photoresist mask as an etching mask, the AlScN layer is etched to transfer the pattern, and the desired AlScN thin film structure is etched; after the etching is completed, a degluing process is carried out to remove the remaining photoresist. It can be understood that the etching of the AlScN layer can be a plasma etching process or a wet etching process; the degluing process is usually carried out by an ashing process.

[0053] Step 3: Perform post-degluing cleaning treatment on the substrate.

[0054] It can be understood that the post-degluing cleaning of the step is carried out using the cleaning method provided in Embodiment 1.

[0055] By using the cleaning method provided in Embodiment 1, it is possible to effectively remove the etching by-products and the photoresist residues, and at the same time avoid the abnormal cracking on the surface of the AlScN thin film caused by the existing EKC cleaning.

[0056] Embodiment 3

[0057] The present invention also provides a semiconductor structure obtained by the above Embodiment 1 or Embodiment 2. Usually, the obtained AlScN thin film structure is mostly used as a piezoelectric thin film structure in MEMS sensors.

[0058] Some commonly used English nouns or letters used in the present invention for the convenience of clear description are only for exemplary reference rather than restrictive interpretation or specific usage, and the protection scope of the present invention should not be limited by their possible Chinese translations or specific letters.

[0059] It should also be noted that in this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

Claims

1. A method for cleaning an AlScN thin film structure, characterized in that: include: Providing a substrate, on which an AlScN thin film structure is formed, and on which a debonding process has been completed; The substrate is cleaned after degumming using a weak alkaline or neutral cleaning solution.

2. The cleaning method of an AlScN thin film structure according to claim 1, characterized in that: The substrate is cleaned after degumming using an RCA cleaning solution.

3. The cleaning method of an AlScN thin film structure according to claim 2, characterized in that: Using the RCA cleaning solution to clean the substrate after degumming includes: The substrate is first cleaned using SC-1 solution at a cleaning temperature of 70-80°C; Rinse the substrate with deionized water; The substrate was cleaned for the second time using SC-2 solution at a cleaning temperature of 70-80°C.

4. The cleaning method of an AlScN thin film structure according to claim 3, characterized in that: The SC-1 solution is a mixed solution of deionized water, hydrogen peroxide and ammonia water, and the volume ratio of the deionized water: hydrogen peroxide: ammonia water is 5:1:

1.

5. The cleaning method of an AlScN thin film structure according to claim 3, characterized in that: The SC-2 solution is a mixed solution of deionized water, hydrogen peroxide and hydrochloric acid, and the volume ratio of the deionized water: hydrogen peroxide: hydrochloric acid is 6:1:

1.

6. A method for forming an AlScN thin film structure, characterized in that: include: providing a substrate on which an AlScN layer is deposited; Performing a patterning process on the AlScN layer to form an AlScN thin film structure; The substrate is cleaned after degumming according to the cleaning method described in any one of claims 1 to 5.

7. The method for forming an AlScN thin film structure according to claim 6, characterized in that: The AlScN layer is formed by any one of magnetron sputtering, molecular beam epitaxy or metal organic chemical vapor deposition.

8. The method for forming an AlScN thin film structure according to claim 6, characterized in that: The graphical processing includes: forming a photoresist layer on the AlScN layer; Expose and develop the photoresist layer to form a photoresist mask; Using the photoresist mask as an etching mask, etching the AlScN layer to form an AlScN thin film structure; Perform a stripping process to remove the remaining photoresist.

9. The method for forming an AlScN thin film structure according to claim 8, characterized in that: The etching process is a plasma etching process or a wet etching process; the degumming process is an ashing process.

10. A semiconductor structure, characterized in that: Obtained according to the cleaning method described in any one of claims 1-5 or the forming method described in any one of claims 6-9.

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