Cleaning method of CVD (chemical vapor deposition) reaction cavity

Abstract

The invention relates to the technical field of semiconductor preparation, in particular to a cleaning method of a CVD reaction cavity. According to the cleaning method, a first cleaning stage, a second cleaning stage and a third cleaning stage are sequentially carried out according to a time sequence, in the first cleaning stage, first mixed gas of C2F6 and O2 is introduced into a reaction cavity, and the first mixed gas is made to carry out reaction cleaning on a deposited film on the inner wall face of the reaction cavity; in the second cleaning stage, second mixed gas of NF3 and O2 is introduced into the reaction cavity, so that the second mixed gas reacts and cleans the deposited film after the first cleaning stage; in the third cleaning stage, third mixed gas of C2F6, NF3, O2 and He is introduced into the reaction cavity, the third mixed gas conducts reaction cleaning on the deposited film after the second cleaning stage, the reaction rate of the first mixed gas and the deposited film is larger than the reaction rate of the second mixed gas and the deposited film, the third mixed gas is excessive reaction, and the deposited film after the second cleaning stage is subjected to reaction cleaning. According to the cleaning method, the deposited film in the CVD reaction cavity can be efficiently cleaned.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor preparation, and in particular to a cleaning method for a CVD reaction chamber. Background Art

[0002] In the field of power semiconductors, compared with traditional silicon-based devices, silicon carbide devices have many advantages such as low leakage current, resistance to high temperature and high pressure, low on-resistance, fast switching speed, and low operating loss. They have broad application prospects in new energy vehicles, photovoltaic power generation, rail transit, smart grids and other fields.

[0003] In recent years, domestic silicon carbide power devices have developed rapidly. Unlike traditional silicon-based chips, in the field of silicon carbide chip manufacturing, due to differences in substrates, many chip manufacturing processes cannot directly draw on the experience of silicon-based chip manufacturing, but need to be continuously explored and optimized in the actual production practice process.

[0004] In the traditional silicon power device process, high-temperature diffusion and ion implantation are the two main doping methods. Doping elements such as nitrogen (N), phosphorus (P), aluminum (Al) and boron (B) require extremely high temperatures above 2000°C in SiC to obtain a suitable diffusion coefficient, and such high-temperature diffusion will bring many problems: high temperature will introduce a variety of diffusion defects, deteriorate the electrical performance of the device, and cannot use common photoresists as masks, etc. Therefore, SiC doping can only choose ion implantation process.

[0005] Before ion implantation, SiO2 deposited by a PECVD (chemical CVD deposition) machine is usually required as a hard mask to act as a barrier layer for ion implantation, and thick film SiO2 must be selected. The thick film SiO2 process is best with PECVD, which has the characteristics of rapid film formation and good uniformity, but the process also has corresponding limitations, that is, a large amount of attachments will be generated in the cavity after deposition, and the cleanliness of the attachments will affect the defects of the film formation process. For example, if the cleaning amount is insufficient, the attachments in the cavity will fall to the surface of the wafer during the film formation process, resulting in dust in or on the SiO2 film. In addition, the attachments will cause the nozzle to be blocked, resulting in changes in the gas flow rate, thereby affecting the quality of the deposition film. The cavity environment deteriorates faster, shortening the PM cycle. Excessive cleaning will cause ineffective consumption of materials, and excessive cleaning will also affect the life of the cavity. Therefore, the cleaning of the cavity after deposition is crucial.

[0006] At present, in order to ensure thorough cleaning, the average cleaning rate is tested to confirm the cleaning time under the film thickness, and then based on this, after the wafer is deposited, 40%-80% of the over-cleaning amount is increased to ensure that there is no residual SiO2 affecting the next deposition. However, too much over-cleaning will damage the CVD reaction chamber, resulting in changes in the surface chemical properties of the reaction chamber, such as surface roughness, hydrophilicity, etc. This will not only affect the adsorption and deposition of reactants on the surface of the chamber in the subsequent process, affecting the stability of the entire process and product quality, but will also damage the CVD reaction chamber. Summary of the invention

[0007] The purpose of the present invention is to avoid the shortcomings of the prior art and provide a cleaning method for a CVD reaction chamber, which can efficiently clean the deposited film in the CVD reaction chamber and effectively protect the wall surface of the reaction chamber, and has the advantage of low cost.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A CVD reaction chamber cleaning method is provided, wherein a first cleaning stage, a second cleaning stage and a third cleaning stage are performed in chronological order.

[0010] That is, the first cleaning stage is performed first, then the second cleaning stage is performed, and finally the third cleaning stage is performed. In actual production, after the first cleaning stage, the second cleaning stage and the third cleaning stage are completed, the film deposition process is performed and the first cleaning stage is cycled.

[0011] The steps of the first cleaning stage include: introducing a first mixed gas of C2F6 and O2 into the reaction chamber, so that the first mixed gas reacts and cleans the deposited film on the inner wall of the reaction chamber;

[0012] After C2F6 and O2 are mixed, they are used as the first mixed gas, so that the first mixed gas first reacts with the deposited film on the inner wall of the reaction chamber. In essence, the deposited film is removed by reacting in a chemical reaction manner.

[0013] The steps of the second cleaning stage include: introducing a second mixed gas of NF3 and O2 into the reaction chamber, so that the second mixed gas reacts and cleans the deposited film after the first cleaning stage;

[0014] After NF3 and O2 are mixed, they are used as the second mixed gas, so that the second mixed gas first reacts with the deposited film on the inner wall of the reaction chamber. In essence, the deposited film is removed by reacting in a chemical reaction manner.

[0015] The steps of the third cleaning stage include: introducing a third mixed gas of C2F6, NF3, O2 and He into the reaction chamber, so that the third mixed gas reacts and cleans the deposited film after the second cleaning stage,

[0016] C2F6, NF3, O2 and He are mixed as the third mixed gas, so that the third mixed gas first reacts with the deposited film on the inner wall of the reaction chamber. In essence, the deposited film is removed by chemical reaction.

[0017] The reaction rate of the first mixed gas with the deposition film is greater than the reaction rate of the second mixed gas with the deposition film, and the third mixed gas reacts excessively with the deposition film in the reaction chamber.

[0018] By adjusting the reaction rate of the first mixed gas and the deposited film to be greater than the reaction rate of the second mixed gas and the deposited film, the first cleaning stage can perform preliminary and extensive cleaning, the second cleaning stage is slow cleaning, and the uncleaned parts of the second cleaning stage are cleaned, and the third cleaning stage is excessive cleaning, and a thorough cleaning is performed. Through the three-stage step-by-step cleaning, the use of a certain special gas can be effectively saved, and costs can be saved. At the same time, the time of excessive cleaning can also be reduced, thereby protecting the reaction chamber and extending the service life of the reaction chamber.

[0019] The cleaning amount of the deposited film on the inner wall of the reaction chamber in each cleaning stage is respectively:

[0020] The cleaning amount Q1 of the first cleaning stage is 70-90%;

[0021] The cleaning amount Q2 of the second cleaning stage is 5-40%;

[0022] The cleaning amount Q3 in the third cleaning stage is 5-10%.

[0023] Since the film thickness deposited in the reaction chamber is consistent with the product CVD deposited film thickness, the cleaning amount of the deposited film on the inner wall of the reaction chamber is calculated based on the inner surface area of ​​the reaction chamber and the product deposited film thickness.

[0024] During the cleaning process, the thickness of the deposited film in the reaction chamber can be detected to know the cleaning amount at each stage. By limiting the cleaning amount range, the cleaning endpoint of each stage can be effectively known, thereby increasing controllability.

[0025] In some embodiments, during the first cleaning stage, the radio frequency power supply is turned on, so that the plasma excitation frequency is 13.56 MHz to 60 MHz, and the radio frequency power is 700 W to 1300 W.

[0026] Enables fast response in the first cleaning stage.

[0027] In some embodiments, during the first cleaning stage, the cleaning time is determined by:

[0028] First, the SiO2 film on the wafer is cleaned for a cleaning time of T1, and then the cleaning time T2 is determined according to the degree of cleaning.

[0029] The calculation formula of T2 is:

[0030] T2=T1 / (D1-D2)D*Q1

[0031] in,

[0032] D is the thickness of the deposited film deposited by CVD on the product

[0033] D1 is the SiO2 thickness on the wafer before cleaning;

[0034] D2 is the SiO2 thickness on the wafer after cleaning time T1,

[0035] The obtained T1 and T2 are the time required for cleaning the reaction chamber in the first cleaning stage.

[0036] In some embodiments, in the first cleaning stage, the C2F6 gas flow rate is 400-1000 sccm, the O2 gas flow rate is 400-1000 sccm, and the temperature of the reaction chamber is 300°C-450°C.

[0037] Enables fast response cleaning in the first cleaning stage.

[0038] In some embodiments, during the second cleaning stage, the radio frequency power supply is turned on to make the plasma excitation frequency 13.56 MHz to 60 MHz and the radio frequency power 600 W to 1000 W.

[0039] The second cleaning stage achieves a slow-reacting cleaning.

[0040] In some embodiments, during the second cleaning stage, the cleaning time is determined by:

[0041] First, the SiO2 film on the wafer is cleaned for a cleaning time of T3, and then the cleaning time T4 is determined according to the degree of cleaning.

[0042] The calculation formula of T4 is:

[0043] T4=T3 / (D3-D4)D*Q2

[0044] in,

[0045] D is the thickness of the deposited film deposited by CVD on the product

[0046] D3 is the SiO2 thickness on the wafer after the first cleaning stage;

[0047] D4 is the SiO2 thickness on the wafer after cleaning time T3;

[0048] The obtained T3 and T4 are the time required for cleaning the reaction chamber in the second cleaning stage.

[0049] In some embodiments, in the second cleaning stage, the C2F6 gas flow rate is 100-400 sccm, the O2 gas flow rate is 100-400 sccm, and the temperature of the reaction chamber is set to 300°C-450°C.

[0050] The second cleaning stage achieves a slow-reacting cleaning.

[0051] In some embodiments, during the second cleaning stage, the radio frequency power supply is turned on to make the plasma excitation frequency 13.56 MHz to 60 MHz and the radio frequency power 600 W to 1000 W.

[0052] In some embodiments, during the third cleaning stage, the cleaning time is determined by:

[0053] First, the SiO2 film on the wafer is cleaned for a cleaning time of T5, and then the cleaning time T6 is determined according to the degree of cleaning.

[0054] The calculation formula of T6 is:

[0055] T6=T5 / (D5-D6)D*Q3

[0056] in,

[0057] D is the thickness of the deposited film deposited by CVD on the product

[0058] D3 is the SiO2 thickness on the wafer after the second cleaning stage;

[0059] D4 is the SiO2 thickness on the wafer after cleaning time T5;

[0060] The obtained T5 and T6 are the time required for cleaning the reaction chamber in the third cleaning stage.

[0061] In some embodiments, in the third cleaning stage, the NF3 gas flow rate is 100-500 sccm, the C2F6 gas flow rate is 200-1000 sccm, the O2 gas flow rate is 200-1000 sccm, and the temperature of the reaction chamber is set to 300°C-450°C.

[0062] The third cleaning stage is used to achieve excess reaction cleaning.

[0063] In some embodiments, during each cleaning stage, the pressure in the reaction chamber is maintained at 2 torr to 6 torr.

[0064] In some embodiments, after each cleaning stage is completed, the gas in the reaction chamber is evacuated.

[0065] After each cleaning stage is completed, the gas in the reaction chamber is evacuated to prevent the cleaning gas of the previous stage from affecting the cleaning of the next stage.

[0066] The beneficial effects of the cleaning method of a CVD reaction chamber of the present invention are as follows:

[0067] The cleaning method of the CVD reaction chamber of the present invention disassembles the cleaning steps of the reaction chamber after the CVD deposition film into a first cleaning stage of rapid cleaning, a second cleaning stage of slow cleaning, and a third cleaning stage of excessive cleaning. The cleaning gas in the first cleaning stage is C2F6, which decomposes in a plasma environment to produce active particles such as fluorine free radicals. These fluorine free radicals attack the silicon-oxygen bonds in SiO2, break the silicon-oxygen bonds, and form volatile fluorine-containing compounds SiF4, thereby removing SiO2. The cleaning gas in the second cleaning stage is NF3, which dissociates in plasma to form fluorine-containing active groups and nitrogen-containing active groups. The fluorine-containing active groups can break the silicon-oxygen bonds in SiO2 like the fluorine free radicals produced by the decomposition of C2F6, forming volatile SiF4, thereby removing SiO2. The cleaning gas of the third cleaning stage introduces NF3 and C2F6 at the same time. Under the mixed effect of the two, the attachments in different states of the cavity can be cleaned and the areas that are difficult to clean can be strengthened. The process has good effect and takes a short time, which can reduce the damage to the cavity kit. By adjusting the reaction rate of the first mixed gas and the deposition film to be greater than the reaction rate of the second mixed gas and the deposition film, the first cleaning stage can perform preliminary and substantial cleaning, the second cleaning stage is slow cleaning, and the uncleaned parts of the second cleaning stage are cleaned. The third cleaning stage is excessive cleaning, and a thorough cleaning is performed. Through the three-stage step-by-step cleaning, the use of a certain special gas can be effectively saved, and the cost can be saved. At the same time, the time of excessive cleaning can be reduced, the reaction chamber can be protected, and the service life of the reaction chamber can be extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is a structural schematic diagram of a cleaning method for a CVD reaction chamber according to embodiment 1 of the present invention.

[0069] Figure 2 It is a structural schematic diagram of a cleaning method for a CVD reaction chamber according to Embodiment 2 of the present invention.

[0070] Figure 3 This is the effect of the wafer produced after the traditional cleaning reaction chamber.

[0071] Figure 4This is a rendering of the wafer obtained after cleaning the reaction chamber in Example 2.

[0072] Figure 5 This is a comparison chart of particles on the surface of the wafer obtained 30 days after the conventional cleaning of the reaction chamber and after the cleaning of the reaction chamber in Example 2.

[0073] Figure 6 This is a comparison chart of the PM frequency in the chamber 30 days after the conventional cleaning of the reaction chamber and after the cleaning of the reaction chamber in Example 2. DETAILED DESCRIPTION

[0074] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0075] The terms used in the present invention are only for the purpose of describing specific implementation regulations, and are not intended to limit the present invention. The singular forms "a", "the" used in the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used in this article refers to and includes any or all possible combinations of one or more associated listed items.

[0076] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0077] Example 1

[0078] In the process of manufacturing silicon carbide chips, the hard mask layer is used as a barrier layer for ion implantation, and thick SiO2 film needs to be selected. The thick SiO2 film process is optimized with PECVD, which has the characteristics of fast film formation and good uniformity, but the process also has corresponding limitations, that is, a large amount of attachments will be generated in the cavity after deposition, and the cleanliness of the attachments will affect the defects of the film formation process. For example, if the cleaning amount is insufficient, the attachments in the cavity will fall to the surface of the wafer during the film formation process, resulting in dust in or on the SiO2 film. In addition, the attachments will cause the nozzle to be blocked, resulting in changes in the gas flow rate, thereby affecting the quality of the deposition. The cavity environment deteriorates faster, shortening the PM cycle. Excessive cleaning will cause ineffective consumption of materials, and excessive cleaning will also affect the life of the cavity. Therefore, the cleaning of the cavity after deposition is crucial.

[0079] For the above technical issues, please refer to Figure 1 , this embodiment discloses:

[0080] The cleaning method of the CVD reaction chamber includes performing a first cleaning stage, a second cleaning stage and a third cleaning stage in chronological order.

[0081] That is, the first cleaning stage is performed first, then the second cleaning stage is performed, and finally the third cleaning stage is performed. In actual production, after the first cleaning stage, the second cleaning stage and the third cleaning stage are completed, the film deposition process is performed and the first cleaning stage is cycled.

[0082] The steps of the first cleaning stage include: introducing a first mixed gas of C2F6 and O2 into the reaction chamber, so that the first mixed gas reacts and cleans the deposited film on the inner wall of the reaction chamber;

[0083] After C2F6 and O2 are mixed, they are used as the first mixed gas, so that the first mixed gas first reacts with the deposited film on the inner wall of the reaction chamber. In essence, the deposited film is removed by reacting in a chemical reaction manner.

[0084] The steps of the second cleaning stage include: introducing a second mixed gas of NF3 and O2 into the reaction chamber, so that the second mixed gas reacts and cleans the deposited film after the first cleaning stage;

[0085] After NF3 and O2 are mixed, they are used as the second mixed gas, so that the second mixed gas first reacts with the deposited film on the inner wall of the reaction chamber. In essence, the deposited film is removed by reacting in a chemical reaction manner.

[0086] The steps of the third cleaning stage include: introducing a third mixed gas of C2F6, NF3, O2 and He into the reaction chamber, so that the third mixed gas reacts and cleans the deposited film after the second cleaning stage,

[0087] C2F6, NF3, O2 and He are mixed as the third mixed gas, so that the third mixed gas first reacts with the deposited film on the inner wall of the reaction chamber. In essence, the deposited film is removed by chemical reaction.

[0088] The reaction rate of the first mixed gas with the deposition film is greater than the reaction rate of the second mixed gas with the deposition film, and the third mixed gas reacts excessively with the deposition film in the reaction chamber.

[0089] By adjusting the reaction rate of the first mixed gas and the deposited film to be greater than the reaction rate of the second mixed gas and the deposited film, the first cleaning stage can perform preliminary and extensive cleaning, the second cleaning stage is slow cleaning, and the uncleaned parts of the second cleaning stage are cleaned, and the third cleaning stage is excessive cleaning, and a thorough cleaning is performed. Through the three-stage step-by-step cleaning, the use of a certain special gas can be effectively saved, and costs can be saved. At the same time, the time of excessive cleaning can also be reduced, thereby protecting the reaction chamber and extending the service life of the reaction chamber.

[0090] The cleaning amount of the deposited film on the inner wall of the reaction chamber in each cleaning stage is respectively:

[0091] The cleaning amount Q1 of the first cleaning stage is 70-90%;

[0092] The cleaning amount Q2 of the second cleaning stage is 5-40%;

[0093] The cleaning amount Q3 in the third cleaning stage is 5-10%.

[0094] Since the film thickness deposited in the reaction chamber is consistent with the CVD film thickness of the corresponding product, the cleaning amount of the deposited film on the inner wall of the reaction chamber is calculated based on the inner surface area of ​​the reaction chamber and the thickness of the deposited film of the product.

[0095] During the cleaning process, the thickness of the deposited film in the reaction chamber can be detected to know the cleaning amount at each stage. By limiting the cleaning amount range, the cleaning endpoint of each stage can be effectively known, thereby increasing controllability.

[0096] In this embodiment, during the first cleaning stage, the radio frequency power supply is turned on, so that the plasma excitation frequency is 13.56 MHz to 60 MHz, and the radio frequency power is 700 W to 1300 W.

[0097] Enables fast response in the first cleaning stage.

[0098] Since the changes in the deposited film in the reaction chamber cannot be observed well, and the thickness of the deposited film on the wafer is actually consistent with the thickness of the deposited film in the reaction chamber, in order to accurately grasp the response time to the reaction chamber, the time required to clean the deposited film on the wafer is first tested, and then the time on the cleaned wafer is used as the time to clean the reaction chamber.

[0099] In this embodiment, in the first cleaning stage, the cleaning time for the deposited SiO2 film wafer is T1, and then the cleaning time T2 is determined according to the cleaning degree.

[0100] The calculation formula of T2 is:

[0101] T2=T1 / (D1-D2)D*Q1

[0102] in,

[0103] D is the thickness of the deposited film deposited by CVD on the product

[0104] D1 is the SiO2 thickness on the wafer before cleaning;

[0105] D2 is the SiO2 thickness on the wafer after cleaning time T1,

[0106] The obtained T1 and T2 are the time required for cleaning the reaction chamber in the first cleaning stage.

[0107] In this embodiment, in the first cleaning stage, the C2F6 gas flow rate is 400-1000 sccm, the O2 gas flow rate is 400-1000 sccm, and the temperature of the reaction chamber is 300°C-450°C.

[0108] Enables fast response cleaning in the first cleaning stage.

[0109] In this embodiment, during the second cleaning stage, the radio frequency power supply is turned on, so that the plasma excitation frequency is 13.56 MHz to 60 MHz, and the radio frequency power is 600 W to 1000 W.

[0110] The second cleaning stage achieves a slow-reacting cleaning.

[0111] In this embodiment, in the second cleaning stage, the cleaning time for the deposited SiO2 film wafer is T3, and then the cleaning time T4 is determined according to the cleaning degree.

[0112] The calculation formula of T4 is:

[0113] T4=T3 / (D3-D4)D*Q2

[0114] in,

[0115] D is the thickness of the deposited film deposited by CVD on the product

[0116] D3 is the SiO2 thickness on the wafer after cleaning;

[0117] D4 is the SiO2 thickness on the wafer after cleaning time T3,

[0118] The obtained T3 and T4 are the time required for cleaning the reaction chamber in the second cleaning stage.

[0119] In this embodiment, in the second cleaning stage, the C2F6 gas flow rate is 100-400 sccm, the O2 gas flow rate is 100-400 sccm, and the temperature of the reaction chamber is set to 300°C-450°C.

[0120] The second cleaning stage achieves a slow-reacting cleaning.

[0121] In this embodiment, during the second cleaning stage, the radio frequency power supply is turned on, so that the plasma excitation frequency is 13.56 MHz to 60 MHz, and the radio frequency power is 600 W to 1000 W.

[0122] In this embodiment, during the third cleaning stage, the cleaning time for the deposited SiO2 film wafer is T5, and then the cleaning time T6 is determined according to the cleaning degree.

[0123] The calculation formula of T6 is:

[0124] T6=T5 / (D5-D6)D*Q3

[0125] in,

[0126] D is the thickness of the deposited film deposited by CVD on the product

[0127] D5 SiO2 thickness on wafer before cleaning;

[0128] D6 is the SiO2 thickness on the wafer after cleaning time T5,

[0129] The obtained T5 and T6 are the time required for cleaning the reaction chamber in the third cleaning stage.

[0130] In this embodiment, in the third cleaning stage, the NF3 gas flow rate is 100-500 sccm, the C2F6 gas flow rate is 200-1000 sccm, the O2 gas flow rate is 200-1000 sccm, and the temperature of the reaction chamber is set to 300°C-450°C.

[0131] The third cleaning stage is used to achieve excess reaction cleaning.

[0132] In this embodiment, during each cleaning stage, the pressure in the reaction chamber is maintained at 2 torr to 6 torr.

[0133] In this embodiment, after each cleaning stage is completed, the gas in the reaction chamber is evacuated.

[0134] After each cleaning stage is completed, the gas in the reaction chamber is evacuated to prevent the cleaning gas of the previous stage from affecting the cleaning of the next stage.

[0135] Example 2

[0136] To further illustrate the specific embodiments of the present invention, please refer to Figure 2 , this embodiment discloses an implementation method of depositing SiO2.

[0137] After the PECVD machine deposits the hard mask on the wafer, a layer of SiO2 will also adhere to the inner wall of the chamber. The thickness of this SiO2 layer is proportional to the thickness of the deposited hard mask layer. The stability of the chamber environment is an important prerequisite for the stability of the process quality. It is necessary to ensure the consistency of the chamber environment as much as possible during each deposition. Therefore, it is very important to clean the chamber after each deposition. The SiO2 on the inner wall of the chamber needs to be removed to ensure that the chamber environment is consistent during the next deposition.

[0138] However, in order to ensure thorough cleaning, the average cleaning rate of the cleaning menu is tested to confirm the cleaning time under the film thickness. Then, based on this, after the wafer is deposited, 40% to 80% of the over-cleaning amount is increased to ensure that there is no residual SiO2 affecting the next deposition. However, too much over-cleaning will damage the cavity part and change the surface chemical properties of the cavity, such as surface roughness, hydrophilicity, etc. This will not only affect the adsorption and deposition of reactants on the cavity surface in the subsequent process, affecting the stability of the entire process and product quality, but also damage the life of the cavity part.

[0139] This embodiment is aimed at the thick film process of the PECVD machine. By optimizing and adjusting the cleaning process flow of the cavity after film deposition, the cleaning effect is improved, the maintenance cycle of the cavity is extended, and the production efficiency is improved. It has a significant effect on thick films (thickness range is 1 to 3 um). The specific steps of the cleaning process of the present invention are described as follows:

[0140] First cleaning stage: quick cleaning

[0141] CVD chamber clean1: C2F6 is used as the cleaning gas, and the cleaning amount of this process accounts for 70-90% of the total cleaning amount. C2F6 will decompose in the plasma environment to produce active particles such as fluorine free radicals. These fluorine free radicals attack the silicon-oxygen bonds in SiO2, breaking the silicon-oxygen bonds to form volatile fluorine-containing compounds SiF4, thereby removing SiO2. The reaction equation is as follows:

[0142] SiO2+4F·→SiF4+2O·

[0143] Specific implementation steps: After the thick film D is deposited on the wafer, the wafer is transferred out of the chamber, and the cleaning gases C2F6 and O2 are introduced into the chamber. When the chamber pressure is stabilized at the set value P1, the RF power supply RF1 is turned on to start cleaning the chamber, and the time is set to T2.

[0144] Specific parameter settings: C2F6 gas flow rate is 400-1000sccm, O2 gas flow rate is 400-1000sccm, chamber pressure is set to 4±2Torr, plasma excitation frequency is 13.56MHz~60MHz, RF power is 1000±300W, and chamber temperature is 300-450℃. The reaction time needs to be determined according to the actual experimental results. The experimental plan is as follows: Assuming that the thickness of the deposited hard mask is D, a SiO2 film is deposited on a wafer using a PECVD machine, and the SiO2 film thickness is measured to be D1. The wafer is reacted under the above reaction conditions for a period of time T1 (at least 30s), and then the SiO2 film thickness after cleaning is measured D2. Based on this, the reaction time T2 of the above reaction conditions is determined. The calculation formula is as follows:

[0145] T2=T1 / (D1-D2)D*70~90%

[0146] CVD chamber pump down 1:

[0147] After reaching the set reaction time, stop introducing the cleaning gas, use the pump to perform vacuum treatment on the chamber, and pump the chamber reactants after Clean1 to the tail exhaust.

[0148] Second cleaning stage: Slow cleaning

[0149] CVD chamber clean 2: NF3 is used as the cleaning gas in this process, and the cleaning amount of this process accounts for 10-40% of the total cleaning amount. NF3 dissociates in the plasma to form fluorine-containing active groups and nitrogen-containing active groups. The fluorine-containing active groups can break the silicon-oxygen bond in SiO2 like the fluorine free radicals generated by the decomposition of C2F6, forming volatile SiF4, thereby removing SiO2. The reaction equation is as follows:

[0150] SiO2+4F·→SiF4+2O·

[0151] The principle is similar to that of C2F6, but the actual effect is different. The reaction rate of NF3 in removing SiO2 is slower than that of C2F6. The decomposition process of NF3 may be relatively more complicated, and the presence of the nitrogen-containing active groups formed will affect the reaction rate of fluorine free radicals and SiO2 to a certain extent. In addition, the addition of He also slows down the etching rate to a certain extent, increases the stability and uniformity of etching, and ensures that the residual SiO2 can be evenly removed.

[0152] Specific implementation steps: Cleaning gases NF3 and O2 are introduced into the cavity. When the cavity pressure is stabilized at the set value P2, the radio frequency power supply RF2 is turned on to start cleaning the cavity, and the time is set to T4.

[0153] Specific parameter settings: NF3 gas flow rate is 100-400sccm, O2 gas flow rate is 100-400sccm, chamber pressure is set to 4±2Torr, plasma excitation frequency is 13.56MHz~60MHz, RF power is 800±200W, and chamber temperature is 300-450℃. The reaction time also needs to be determined according to the actual experimental results. Experimental plan: Assuming that the thickness of the deposited hard mask is D, a SiO2 film is deposited on a wafer using a PECVD machine, and the SiO2 film thickness is measured to be D3. The wafer is reacted under the above reaction conditions for a period of time T3 (at least 30s), and then the SiO2 film thickness after cleaning is measured to be D4. Based on this, the reaction time T4 of the above reaction conditions is determined. The calculation formula is as follows:

[0154] T4=T3 / (D3-D4)D*10~40%

[0155] CVD chamber pump down 2:

[0156] After reaching the set reaction time, stop introducing the cleaning gas, use the pump to perform vacuum treatment on the chamber, and pump the chamber reactants after Clean2 to the tail exhaust.

[0157] Third cleaning stage: Excess cleaning:

[0158] CVD chamber clean 3: In this process, NF3 and C2F6 are introduced at the same time. The mixed effect of the two can clean the attachments in different states of the chamber and strengthen the cleaning of the areas that are difficult to clean. This process has good effect, takes a short time, and can reduce damage to the chamber kit.

[0159] Specific implementation steps: C2F6, NF3, O2, and He are introduced into the chamber at the same time. The cleaning amount in this process accounts for 5%-10% of the total cleaning amount. When the chamber pressure is stabilized at the set value P3, the radio frequency power supply RF3 is turned on to start cleaning the chamber, and the time is set to T6.

[0160] Specific parameter settings: NF3 gas flow rate is 100-500sccm, C2F6 gas flow rate is 200-1000sccm, O2 gas flow rate is 200-1000sccm, He gas flow rate is 400-2000sccm, chamber pressure is set to 4±2Torr, plasma excitation frequency is 13.56MHz~60MHz, RF power is 800±200W, and chamber temperature is 300-450℃. The reaction time also needs to be determined according to the actual experimental results. Experimental plan: Assuming that the thickness of the deposited hard mask is D, a SiO2 film is deposited on a wafer using a PECVD machine, and the SiO2 film thickness is measured to be D5. The wafer is reacted under the above reaction conditions for a period of time T5 (at least 30s), and then the SiO2 film thickness after cleaning is measured to be D6. Based on this, the reaction time T6 of the above reaction conditions is determined. The calculation formula is as follows:

[0161] T6=T5 / (D5-D6)D*5~10%

[0162] CVD chamber pump down 3:

[0163] After reaching the set reaction time, stop introducing the cleaning gas, use the pump to vacuum the chamber, and pump the chamber reactants after Clean3 to the tail exhaust.

[0164] The reaction rate of Clean 1 in this embodiment is relatively fast, and the etching uniformity is relatively poor. The main purpose of this process is to remove most of the SiO2 film attached to the inner wall of the cavity;

[0165] Clean 2 has a relatively slow reaction rate, but has a higher cleaning ability. It can alleviate the uneven surface after Clean 1 cleaning to a certain extent, and can basically effectively remove the residual SiO2, making the entire residual surface smoother;

[0166] The response of Clean 3 is to combine two different effects, perform a final cleaning on some hard-to-clean areas in the cavity space, and ensure a certain degree of excess cleaning to ensure the cleaning effect of the cavity.

[0167] This implementation significantly reduces the particle problem in the deposition process and greatly improves the cleaning efficiency of the reaction chamber, thereby improving the machine capacity utilization rate by improving the thick film hard mask process in the SiC process flow, namely the post-deposition chamber cleaning process of the PECVD machine. Compared with the traditional cleaning method, this embodiment not only reduces the use of special gases and avoids excessive cleaning, but also greatly reduces the damage to the chamber while ensuring the cleaning intensity. The inner wall of the reaction chamber can remain clean for a long time, which extends the preventive maintenance cycle of the chamber, increases the batch of operations within a cycle, and effectively reduces the equipment maintenance cost.

[0168] Effect comparison

[0169] After the machine has operated 1000 wafers, the data of the newly added particles collected after operating 10 wafers continuously are as follows:

[0170] The traditional method of cleaning the reaction chamber has the following cleaning effects: Figure 3 The cleaning effect of the reaction chamber in the embodiment 2 is shown as follows: Figure 4 As shown, it can be seen that the cleaning effect of the present embodiment 2 is significantly better than the traditional cleaning effect, and there are almost no particles distributed on the surface of the wafers made in the reaction chamber after cleaning according to the present embodiment 2.

[0171] Further,

[0172] The effect of cleaning the reaction chamber by the traditional method was compared with that by Example 2. The number of hard mask film particles added during the CVD chamber operation and the number of chamber operations during the PM were monitored for 30 days. Figure 5 , 6 As shown, it can be seen that the cleaning effect of the present invention is better than that of the traditional cleaning effect.

[0173] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps described in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0174] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0175] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0176] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0177] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for cleaning a CVD reaction chamber, characterized in that: Carry out the first cleaning stage, the second cleaning stage and the third cleaning stage in chronological order. The steps of the first cleaning stage include: introducing a first mixed gas of C2F6 and O2 into the reaction chamber, so that the first mixed gas reacts and cleans the deposited film on the inner wall of the reaction chamber; The steps of the second cleaning stage include: introducing a second mixed gas of NF3 and O2 into the reaction chamber, so that the second mixed gas reacts and cleans the deposited film after the first cleaning stage; The steps of the third cleaning stage include: introducing a third mixed gas of C2F6, NF3, O2 and He into the reaction chamber, so that the third mixed gas reacts and cleans the deposited film after the second cleaning stage, The reaction rate of the first mixed gas with the deposition film is greater than the reaction rate of the second mixed gas with the deposition film, and the third mixed gas reacts excessively with the deposition film in the reaction chamber.

2. The cleaning method of the CVD reaction chamber according to claim 1, characterized in that: The cleaning amount of the deposited film on the inner wall surface of the reaction chamber in each cleaning stage is respectively: The cleaning amount Q1 of the first cleaning stage is 70% to 90%; The cleaning amount Q2 of the second cleaning stage is 5% to 40%; The cleaning amount Q3 in the third cleaning stage is 5% to 10%.

3. The cleaning method of the CVD reaction chamber according to claim 2, characterized in that: In the first cleaning stage, the radio frequency power supply is turned on, so that the plasma excitation frequency is 13.56 MHz to 60 MHz and the radio frequency power is 700 W to 1300 W.

4. The cleaning method of a CVD reaction chamber according to claim 2, characterized in that: During the first cleaning stage, the cleaning time is determined by: First, the SiO2 film on the wafer is cleaned for a cleaning time of T1, and then the cleaning time T2 is determined according to the degree of cleaning. The calculation formula of T2 is: T2=T1 / (D1-D2)D*Q1 in, D is the thickness of the deposited film deposited by CVD on the product D1 is the SiO2 thickness on the wafer before cleaning; D2 is the SiO2 thickness on the wafer after cleaning time T1, The obtained T1 and T2 are the time required for cleaning the reaction chamber in the first cleaning stage.

5. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: In the first cleaning stage, the C2F6 gas flow rate is 400-1000 sccm, the O2 gas flow rate is 400-1000 sccm, and the temperature of the reaction chamber is 300°C-450°C.

6. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: In the second cleaning stage, the radio frequency power supply is turned on, so that the plasma excitation frequency is 13.56 MHz to 60 MHz and the radio frequency power is 600 W to 1000 W.

7. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: During the second cleaning stage, Determine cleaning time as follows: First, the SiO2 film on the wafer is cleaned for a cleaning time of T3, and then the cleaning time T4 is determined according to the degree of cleaning. The calculation formula of T4 is: T4=T3 / (D3-D4)D*Q2 in, D is the thickness of the deposited film deposited by CVD on the product D3 is the SiO2 thickness on the wafer after the first cleaning stage; D4 is the SiO2 thickness on the wafer after cleaning time T3; The obtained T3 and T4 are the time required for cleaning the reaction chamber in the second cleaning stage.

8. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: In the second cleaning stage, the C2F6 gas flow rate is 100-400 sccm, the O2 gas flow rate is 100-400 sccm, and the temperature of the reaction chamber is set to 300°C-450°C.

9. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: In the second cleaning stage, the radio frequency power supply is turned on, so that the plasma excitation frequency is 13.56 MHz to 60 MHz and the radio frequency power is 600 W to 1000 W.

10. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: During the third cleaning stage, the cleaning time is determined by the following method: First, the SiO2 film on the wafer is cleaned for a cleaning time of T5, and then the cleaning time T6 is determined according to the degree of cleaning. The calculation formula of T6 is: T6=T5 / (D5-D6)D*Q3 in, D is the thickness of the deposited film deposited by CVD on the product D3 is the SiO2 thickness on the wafer after the second cleaning stage; D4 is the SiO2 thickness on the wafer after cleaning time T5; The obtained T5 and T6 are the time required for cleaning the reaction chamber in the third cleaning stage.

11. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: In the third cleaning stage, the NF3 gas flow rate is 100-500 sccm, the C2F6 gas flow rate is 200-1000 sccm, the O2 gas flow rate is 200-1000 sccm, and the temperature of the reaction chamber is set to 300°C-450°C.

12. The method for cleaning a CVD reaction chamber according to claim 2, characterized in that: During each cleaning stage, the pressure in the reaction chamber is maintained at 2 torr to 6 torr.

13. The method for cleaning a CVD reaction chamber according to any one of claims 1 to 12, characterized in that: After each cleaning stage is completed, the gas in the reaction chamber is evacuated.

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