Preparation method of protective layer in cavity

Abstract

The invention provides a method for preparing a protective layer in a cavity, which comprises the following steps of: 1, depositing a first film with a first thickness in the cavity; a second step of introducing reaction gas into the cavity to etch the first thin film and generate a second thin film with a second thickness; and repeating the first step and the second step for multiple times to generate a second thin film with a third thickness. According to the method, a compact protection layer is grown in the cavity in an etching and deposition circulation mode, so that the aluminum-based component in the cavity is protected from reacting with gas introduced into the cavity; the protective layer obtained by the preparation method provided by the invention is high in density, firm in combination with the surface of each component and small in thickness, the protective layer does not easily release particles to a processed wafer, the cleanliness of a cavity is improved, the cavity cleaning and maintenance period of a machine table is prolonged, the effective production time of the machine table is prolonged, the production cost of device processing is reduced, and the production efficiency is improved. And the yield of the thin film prepared by the machine table is improved.

Description

Technical Field

[0001] The invention relates to the field of semiconductor process equipment, and in particular to a method for preparing a protective layer in a cavity. Background Art

[0002] Thin film deposition is a crucial process step in chip processing. Various conductive and insulating thin film layers are grown on silicon wafers through deposition processes. PECVD (Plasma Enhanced Chemical Vapor Deposition) generates plasma by adding voltage or discharge current to ionize the gas in the reaction chamber. The ionized gas molecules are accelerated in the electric field to form excited states and ions. These active ions interact with the gas and substrate in the chamber to achieve thin film deposition.

[0003] After the PECVD machine prepares a film of a certain thickness, it is necessary to clean the preparation chamber to prevent the accumulation of too thick a film on the components inside the PECVD chamber, which may cause the subsequent film to fall off during the preparation process, thereby causing abnormal quality of the film deposited on the wafer.

[0004] The components in the chamber of the PECVD machine are made of aluminum-based materials (such as aluminum, aluminum alloy or Al2O3). The existing method of clearing the chamber mainly uses the dissociation of gas NF3 to form F+ ions, and uses the F+ ions to remove the thin film accumulated in the chamber. However, when the F+ ions contact the aluminum-based materials, they will react with the aluminum-based materials to form aluminum fluoride. During the normal film preparation process, aluminum fluoride particles are easily released from the components in the chamber onto the wafer, thereby causing defects. Figure 1 The schematic diagram shows a large number of AlF3 particles appearing on the wafer after a certain period of film preparation in the chamber of the machine. When too many particles fall on the wafer, the film quality will be affected, and in severe cases, the performance of the device will be affected. These quality anomalies include, for example, deposition rate drift, etching rate drift, film uniformity, and etching uniformity.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0006] In view of the problems in the prior art, the purpose of the present invention is to provide a method for preparing a protective layer in a cavity, so as to generate a dense protective layer on each component in the cavity, reduce the release of particles onto the wafer, and improve the yield of thin film preparation.

[0007] An embodiment of the present invention provides a method for preparing a protective layer in a cavity, comprising:

[0008] In a first step, a first film with a first thickness is deposited in the cavity;

[0009] The second step is to introduce a reaction gas into the chamber to etch the first film and form a second film of a second thickness;

[0010] The first step and the second step are repeated multiple times to generate a second film with a third thickness.

[0011] In some embodiments, the first thin film is SiOx.

[0012] In some embodiments, the second thin film is AlF3, Al2O3, or AlN.

[0013] In some embodiments, the third thickness of the second film is 10 nm to 100 nm.

[0014] In some embodiments, the flow rate of the reaction gas during the deposition of the first film is 50 sccm to 100 sccm.

[0015] In some embodiments, the reaction power when depositing the first thin film is 400W-1000W.

[0016] In some implementations, the chamber pressure is 3 Torr to 6 Torr when depositing the first film.

[0017] In some embodiments, the first thickness of the first film is

[0018] In some embodiments, in the second step, the time for forming the second thin film is 10s to 25s.

[0019] In some embodiments, the reaction gas in the second step includes at least one of NF3, O2, and N2.

[0020] The method for preparing the protective layer in the cavity provided by the present invention has the following advantages:

[0021] In the first step, a first film of a first thickness is deposited in the cavity; in the second step, a reaction gas is introduced into the cavity to etch the first film and generate a second film of a second thickness; the first step and the second step are repeated multiple times to generate a second film of a third thickness. A dense film is grown in the cavity using an etching plus deposition cycle mode. First, the first film is deposited by PECVD, and then the first film is bombarded by plasma. When the plasma contacts the chamber device, a second film is generated. During the deposition and etching cycle, the first film on the chamber device and the second film that is not firmly bonded are bombarded, and only the dense second film is retained. After the deposition and etching cycle is completed, a layer of uniform and dense second film is finally retained inside the cavity. The dense film is not easy to release particles to fall onto the wafer during the normal process in the cavity, which can reduce the defects of film preparation and improve the yield of film preparation; at the same time, the thickness of the dense film is small, which can extend the cleaning and maintenance cycle of the machine, improve the effective production time of the machine, improve the production efficiency of the device, and reduce the production cost of device processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objectives and advantages of the present invention will become more apparent from a reading of the detailed description of non-limiting embodiments made with reference to the following accompanying drawings.

[0023] Figure 1 This is a schematic diagram of AlF3 particles appearing in the chamber of an existing PECVD machine;

[0024] Figure 2 It is a schematic diagram of clearing the cavity of a PECVD machine in the prior art;

[0025] Figure 3 It is a schematic diagram of growing a SiO2 protective layer of a preset thickness in a cavity of a PEVD machine in the prior art;

[0026] Figure 4 It is a schematic diagram of a normal process of a PEVD machine in the prior art;

[0027] Figure 5 is a flow chart of a method for preparing a protective layer in a cavity provided by an embodiment of the present invention;

[0028] Figure 6 is a schematic diagram of growing a first thin film SiO2 provided by an embodiment of the present invention;

[0029] Figure 7 It is a schematic diagram of etching a SiO2 film and forming an AlF3 film provided by an embodiment of the present invention;

[0030] Figure 8 is a schematic diagram of generating a second thin film AlF3 of a third thickness inside the cavity;

[0031] Fig. 9 It is a schematic diagram of detecting the particle size of the cavity after preparing the protective layer provided by this embodiment. DETAILED DESCRIPTION

[0032] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present invention will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their repeated description will be omitted.

[0033] In the representations of the present application, the representations with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics represented in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. Moreover, the represented specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples represented in the present application and the features of the different embodiments or examples, unless they contradict each other.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the representation of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0035] It should be further understood that the terms "comprises" and "includes" indicate the presence of features, steps, operations, elements, components, items, kinds, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". Exceptions to this definition will only occur when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way.

[0036] In order to solve the problem mentioned in the background technology that when the aluminum-based material parts in the chamber react with F ions, easily releasable aluminum fluoride particles are generated, the prior art adopts the following method: Figures 2 to 4The method shown prepares a protection layer inside the cavity to cover the aluminum fluoride layer and prevent aluminum fluoride particles on the aluminum fluoride layer from being released onto the wafer. Figure 2 It is a schematic diagram of clearing the cavity of a PECVD machine in the prior art; Figure 3 It is a schematic diagram of growing a SiO2 protective layer of a preset thickness in a cavity of a PEVD machine in the prior art; Figure 4 It is a schematic diagram of a normal process of a PEVD machine in the prior art;

[0037] like Figures 2 to 4 As shown, a cross-sectional schematic diagram of a PECVD chamber is shown. The PECVD chamber includes a shower head 10 located at the top of the chamber, a base 20 located at the bottom of the chamber, and a side wall 30 located on the side of the chamber. The surface of the shower head 10 is filled with densely packed small holes, which are used to uniformly inject the reaction gas into the cavity to ensure that the reaction gas uniformly covers the entire wafer surface and generates a uniform coating. Therefore, when the reaction gas is uniformly injected into the cavity from the small holes on the surface of the shower head 10, under the action of the electric field excited by the radio frequency power supply, the reaction gas decomposes into electrons, ions, and active groups, etc., and chemical reactions occur between these decomposition products to generate crystal nuclei of solid films. The crystal nuclei gradually grow into islands, and the islands continue to grow into continuous thin films. During the growth of the thin film, various by-products gradually detach from the surface of the thin film and are discharged from the cavity under the action of a vacuum pump (not shown in the figure).

[0038] The components in the chamber include but are not limited to electrostatic chuck, nozzle, gas distribution plate, nozzle, electrostatic chuck components, chamber wall, gasket, gasket accessories, gas pipeline, chamber cover, nozzle, base, shield, plasma shield, flow equalizer, cooling base, chamber observation hole, bellows, heating assembly, etc. These components are usually made of aluminum-based materials, so they have high thermal conductivity and corrosion resistance, ensuring the stability and reliability of the machine in high temperature and chemical reaction environment.

[0039] like Figure 2 As shown, NF3 gas is first introduced into the cavity through the shower head 10. The NF3 gas forms plasma F+ ions under the action of the electric field excited by the radio frequency power supply. The F+ ions pre-clean the cavity and remove impurities on the components inside the cavity to ensure the cleanliness of the cavity and prevent impurities from contaminating the cavity. When the impurities on the components are removed, the F+ ions will further contact the aluminum-based materials of the components, and then react to form AlF3 films.

[0040] like Figure 3As shown, TEOS (tetraethoxysilane) gas and O2 gas are introduced into the cavity through the shower head 10. TEOS and oxygen generate plasma and react under the excitation of the radio frequency power supply, and a SiO2 film is generated in the cavity. The SiO2 film will cover the AlF3 film to prevent AlF3 particles from being released onto the wafer during the normal process in the cavity. The thickness of the SiO2 film is about

[0042] like Figure 4 As shown, after the protective film covering AlF3 is formed, the film required for each device can be prepared normally in the cavity, and the wafer 40 is placed on the base 20, and the corresponding film layer is set on the wafer 40 according to the required film type. When preparing the films required for each device, various films in the process will continue to be deposited on the inner wall of the cavity (including the base 20 and the side wall 30). When the thickness of the film accumulated on the inner wall is too thick, it is necessary to clear the cavity again after a certain process time to remove the film layer accumulated on the various components in the cavity to avoid the film layer on the inner wall of the cavity falling off during the normal process, causing film preparation quality problems. The normal process here refers to the process when the cavity prepares the device film. In order to avoid the film on the inner wall of the cavity falling off onto the processed wafer during the normal process, this problem can be improved by shortening the cavity cleaning cycle, but if the cavity cleaning cycle is too short, the film production efficiency will be reduced and the production cost of the device will be increased.

[0043] The above-mentioned SiO2 film covering a certain thickness on the AlF3 film will reduce the release of AlF3 particles onto the processed wafer during the normal process, but will reduce the production efficiency of the machine. To improve this problem, an embodiment of the present invention provides a method for preparing a protective layer in a cavity, which is to coat a dense protective film on each component in the cavity, extend the cavity cleaning cycle, reduce the abnormal rate of the growing film, improve the film production efficiency, and reduce the production cost of the device. Figure 5 FIG. 1 is a flow chart showing a method for preparing a protective layer in a protective cavity provided by an embodiment of the present invention. Figure 5 As shown, the method for preparing the protective layer in the cavity includes the following steps:

[0044] A first step S100 is to deposit a first film of a first thickness in a cavity;

[0045] In the second step S200, a reaction gas is introduced into the chamber to etch the first film and form a second film of a second thickness; the first step S100 and the second step S200 are repeated multiple times to form a second film of a third thickness.

[0046] The present invention utilizes an etching plus deposition cycle mode to grow a dense film in a cavity. First, a first film is deposited by PECVD, and then the first film is bombarded by plasma. When the plasma contacts the chamber device, a second film is generated. During the deposition and etching cycle, the first film on the chamber device and the second film that is not firmly bonded are bombarded, leaving only the dense second film. After the deposition and etching cycle is completed, a dense and uniform second film is finally retained inside the cavity. The dense film is not easy to release particles to fall onto the wafer during the normal process in the cavity, which can reduce the defects of film preparation and improve the yield of film preparation; at the same time, the thickness of the dense film is small, which can extend the cleaning and maintenance cycle of the machine, increase the effective production time of the machine, improve the production efficiency of the device, and reduce the production cost of device processing.

[0047] The embodiment of the present invention takes the case where the first thin film grown is SiO2 and the second thin film is AlF3 as an example to explain in detail how to obtain a dense protective film layer using the preparation method provided by the embodiment of the present invention.

[0048] Figure 6 Figure 2 shows a schematic diagram of depositing SiO2 thin film in a chamber. Figure 6 As shown, TEOS (tetraethoxysilane) gas and O2 gas are introduced into the cavity through the shower head 10. TEOS and oxygen generate plasma and react under the excitation of the radio frequency power supply to form a SiO2 film of a first thickness in the cavity.

[0049] The thickness of SiO2 film is about The specific process parameters for depositing SiO2 film are as follows: the flow rate of TEOS and O2 is 50sccm~100sccm, the reaction power is 400W~1000W, and the chamber pressure is 3Torr~6Torr. Exemplarily, the flow rate of TEOS and O2 can be 60sccm, 70sccm, 80sccm, 90sccm, but not limited thereto. Exemplarily, the reaction power can be 500W, 600W, 700W, 800W, 900W, but not limited thereto. Exemplarily, the chamber pressure is 4Torr, 5Torr, but not limited thereto. Those skilled in the art can set the specific process parameters for growing thin films according to actual needs.

[0050] Figure 7 Schematic diagram of etching SiO2 layer and forming AlF3 film is shown. Figure 7As shown, NF3 gas is introduced into the cavity through the shower head 10. The NF3 gas forms plasma F+ ions under the action of the electric field excited by the radio frequency power supply. The F+ ions will first etch the SiO2 film. When the SiO2 film is completely etched away, the components in the cavity are not covered by the protective layer, and the F+ ions will further contact the aluminum-based material in the cavity. The F+ ions will react with the Al-based material to form an AlF3 film. It should be noted that in order to ensure that the first film is completely etched and the second film is formed, the over-etching is controlled to be about 10%, that is, after the first film is completely etched away in theory, a certain etching time is added. In the embodiment of the present invention, in the second step S200, the time for forming the second film is 10s to 25s. Here, in order to ensure that the SiO2 film is completely etched and the AlF3 film is generated, the time for forming the AlF3 film is 10s to 25s. Exemplarily, the time for forming the AlF3 film is 12s, 14s, 16s, 18s, 20s, 22s, or 24s, but is not limited thereto.

[0051] In another embodiment, O2 is introduced into the chamber while NF3 gas is introduced into the chamber. O2 can increase the etching speed of SiO2 to save time for the second step.

[0052] Further, repeat as Figure 6 The "growing SiO2 thin film" shown in Figure 7 As shown in the "etching SiO2 film and generating AlF3 film", in the second "etching SiO2 film and generating AlF3 film", the F+ ions will not only completely etch the SiO2 film, but also will etch away the AlF3 film which is not firmly bonded and has a loose texture during the first growth, so that the F+ ions will react again with the cavity components of the Al-based material to generate the AlF3 film.

[0053] Furthermore, the first step S100 and the second step S200 are cycled for multiple times, so that the AlF3 film with loose bonding is etched away, and the AlF3 film with strong bonding and dense film quality is slowly generated.

[0054] Figure 8 FIG. 4 is a schematic diagram showing a third thickness AlF3 film finally formed in the cavity. Figure 6 The first step S100 shown and Figure 7 The second step S200 is performed 24 times, and finally a dense and uniform AlF3 protective layer is formed. The thickness of the second thin film AlF3 is controlled to be 10nm to 100nm. Exemplarily, the thickness of the second thin film can be 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, but not limited thereto.

[0055] It should be noted that the number of times the first step S100 and the second step S200 are cycled when growing a uniform and dense second film is controlled according to the thickness of the protective layer finally set, and those skilled in the art can set the number of repeated cycles according to actual needs.

[0056] When a dense AlF3 protective layer of a certain thickness is generated in the cavity, the AlF3 particles in the AlF3 film are tightly combined and are not easily released onto the cavity wafer as the cavity environment changes. Therefore, the number of particles released onto the wafer can be reduced, and the rate of quality abnormalities in the film can be reduced. The thickness of the AlF3 film is less than the thickness of the protective layer required to prepare in the prior art, and the maintenance and cleaning cycles in the cavity can be extended, thereby increasing the effective production time of the PECVD machine, reducing the machine downtime, and improving the machine's production efficiency.

[0057] In order to further confirm the beneficial effect of the protective layer obtained by the preparation method provided in the embodiment of the present invention, a dense and thick AlF3 protective film is formed inside the PECVD machine cavity by using the preparation method provided in the embodiment of the present invention, and the PECVD machine is subjected to normal process for a certain period of time. When the accumulated film thickness on the PECVD machine is Figure 1 When the accumulated film thickness in the test chamber is the same during the particle size test, the particle size test is performed again in the cavity. This is a schematic diagram of testing the particle size of the cavity after preparing the protective layer provided in this embodiment. Fig. 9 As shown in FIG. 1 , the particle size in the PECVD machine chamber in the embodiment of the present invention is less than 100 particles, which is much smaller than Figure 1 The number of particles in the cavity tested in the experiment was greater than 10,000. Therefore, the protective layer obtained by the method for preparing the protective layer in the cavity provided by the embodiment of the present invention can reduce the particles released from the cavity protective layer onto the wafer, improve the cleanliness in the cavity, reduce the abnormal rate of film quality, and improve the film preparation yield.

[0058] Further, the first film in the embodiment of the present invention is SiO2, and in other embodiments the first film may be SiO, and the first film is represented as SiOx herein, and when x is 1, the first film is SiO, and when x is 2, the first film is SiO2. The first film includes but is not limited to SiOx, and those skilled in the art may set the type of the first film according to actual needs.

[0059] In other embodiments, the second film is not limited to the AlF3 film shown above, and the second film may also be Al2O3 or AlN, etc. Those skilled in the art may set the specific type of the second film according to the type of device actually produced by the machine, and no specific limitation is made here.

[0060] For example, when the second film is Al2O3, the gases introduced into the PECVD machine include NF3 and O2. NF3 and O2 form plasma F+ ions and O- ions under the action of the electric field excited by the RF power supply. The F+ ions will first etch the SiO2 film. When the SiO2 film is completely etched away, the components in the cavity are not covered by a protective layer, and the O- ions will further contact the aluminum-based material in the cavity. The O- ions react with the Al-based material to generate an Al2O3 film. The gases involved in the reaction to generate the Al2O3 film are not limited to the above examples. Those skilled in the art can set the specific gases involved in the reaction according to actual needs.

[0061] For example, when the second film is AlN, the gases that can be introduced into the PECVD machine include NF3 and N2. NF3 and N2 form plasma F+ ions and N- ions under the action of the electric field excited by the RF power supply. The F+ ions will first etch the SiO2 film. When the SiO2 film is completely etched away, the components in the cavity are not covered by a protective layer. The N-+ ions will further contact the aluminum-based material in the cavity, and the N- ions will react with the Al-based material to form an AlN film. Components containing aluminum materials can be combined with nitrogen atoms to form an AlN film. The gases involved in the reaction to form the AlN film are not limited to the above examples. Those skilled in the art can set the specific gases participating in the reaction according to actual needs.

[0062] In summary, the method for preparing the protective layer in the cavity provided by the present invention has the following advantages:

[0063] In the first step, a first film of a first thickness is deposited in the cavity; in the second step, a reaction gas is introduced into the cavity to etch the first film and generate a second film of a second thickness; the first step and the second step are repeated multiple times to generate a second film of a third thickness. A dense film is grown in the cavity using an etching plus deposition cycle mode. First, the first film is deposited by PECVD, and then the first film is bombarded by plasma. When the plasma contacts the chamber device, a second film is generated. During the deposition and etching cycle, the first film on the chamber device and the second film that is not firmly bonded are bombarded, and only the dense second film is retained. After the deposition and etching cycle is completed, a layer of dense film is finally retained inside the cavity. The dense film is not easy to release particles to fall onto the wafer during the normal process in the cavity, which can reduce the defects of film preparation and improve the yield of film preparation; at the same time, the thickness of the dense film is small, which can extend the cleaning and maintenance cycle of the machine, improve the effective production time of the machine, improve the production efficiency of the device, and reduce the production cost of device processing.

[0064] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

[0065] Unless otherwise indicated herein, the enumeration of data ranges herein is intended only to be used as a shorthand method for representing each individual value within the range individually, and each individual value is incorporated into this specification as if it were individually described herein. All methods described herein can be performed in any appropriate order, unless otherwise indicated herein or clearly contradictory to the context. Unless otherwise required, the use of any and all examples or illustrative language provided herein is intended only to illustrate certain materials and methods and is not intended to limit the scope. The language in the specification should not be interpreted as indicating that any unclaimed element is essential for the practice of the disclosed materials and methods.

[0066] Although the operations of methods are shown and described herein in a particular order, the order of the operations of each method may be altered such that some operations may be performed in a reverse order or such that some operations may be performed at least partially concurrently with other operations.

[0067] It should be understood that the above description is intended to be illustrative, not restrictive. After reading and understanding the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the present disclosure should be determined with reference to the entire scope of the equivalents authorized by the attached claims together with these claims.

Claims

1. A method for preparing a protective layer in a cavity, characterized in that: include: In a first step, a first film with a first thickness is deposited in the cavity; The second step is to introduce a reaction gas into the chamber to etch the first film and form a second film of a second thickness; The first step and the second step are repeated multiple times to generate a second film with a third thickness.

2. The method for preparing a protective layer in a cavity according to claim 1, characterized in that: The first film is SiO x .

3. The method for preparing a cavity inner protective layer according to claim 1, characterized in that: The second thin film is AlF3, Al2O3, or AlN.

4. The method for preparing the protective layer in the cavity according to claim 2, characterized in that: The third thickness of the second thin film is 10 nm to 100 nm.

5. The method for preparing a cavity inner protective layer according to claim 1, characterized in that: The flow rate of the reaction gas during the deposition of the first thin film is 50 sccm to 100 sccm.

6. The method for preparing the protective layer in the cavity according to claim 5, characterized in that: The reaction power when depositing the first thin film is 400W-1000W.

7. The method for preparing the protective layer in the cavity according to claim 6, characterized in that: The chamber pressure is 3 Torr to 6 Torr when depositing the first film.

8. The method for preparing a protective layer in a cavity according to claim 1, characterized in that: The first thickness of the first film is 9. The method for preparing a protective layer in a cavity according to claim 1, characterized in that: In the second step, the time for forming the second thin film is 10s to 25s.

10. The method for preparing a cavity inner protective layer according to claim 1, characterized in that: The reaction gas in the second step includes at least one of NF3, O2, and N2.

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