Silicon oxide film forming method, silicon oxide film forming apparatus, and silicon oxide film

Abstract

A method for forming a silicon oxide film is provided that can improve the production efficiency of a silicon oxide film in which the change in stress value over time is suppressed. This silicon oxide film forming method includes the steps of introducing a process gas for forming a silicon oxide film onto a substrate (200) to be processed in a process chamber (10) through a gas inlet (35), applying AC power of a first frequency to the gas inlet (35), and applying AC power of a second frequency higher than the first frequency to the gas inlet (35). The steps of applying AC power of the first frequency and applying AC power of the second frequency are alternately switched between.

Description

[Technical Field]

[0001] The present invention relates to a silicon oxide film forming method, a silicon oxide film forming apparatus, and a silicon oxide film. [Background technology]

[0002] BACKGROUND ART Conventionally, a silicon oxide film forming method for forming a silicon oxide film on a substrate is known (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses a silicon oxide film formation method in which a process gas for forming a silicon oxide film on a substrate to be processed in a process chamber is introduced through a gas inlet, a relatively high-frequency AC power is applied to the gas inlet, and a relatively low-frequency AC power is applied to a stage on which the substrate is placed, thereby forming a silicon oxide film on the substrate by a parallel-plate plasma CVD method. Furthermore, in the silicon oxide film formation method of Patent Document 1, after a silicon oxide film is formed on a substrate, a modified layer is formed on the surface of the silicon oxide film by a rare gas plasma treatment in order to suppress changes in the stress value of the silicon oxide film over time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6183965 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned Patent Document 1, in order to suppress the change in stress value of a silicon oxide film over time, a silicon oxide film is formed on a substrate, and then a modified layer is formed on the surface of the silicon oxide film by plasma treatment using a rare gas. Therefore, after the silicon oxide film is formed, a rare gas must be introduced and plasma treatment must be performed to form the modified layer. In this case, in order to form the modified layer on the silicon oxide film, the process gas must be replaced after the silicon oxide film is formed. As a result, it is difficult to improve the production efficiency (throughput) of silicon oxide films in which the change in stress value over time is suppressed. Therefore, it is desirable to improve the production efficiency of silicon oxide films in which the change in stress value over time is suppressed.

[0006] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a silicon oxide film forming method and a silicon oxide film forming apparatus that can improve the production efficiency of silicon oxide films in which changes in stress value over time are suppressed. [Means for solving the problem]

[0007] In order to achieve the above object, the inventors of the present application conducted extensive research and found that by providing a process for introducing a process gas for forming a silicon oxide film onto a substrate to be processed in a processing chamber from a gas inlet, a process for applying AC power of a first frequency to the gas inlet, and a process for applying AC power of a second frequency higher than the first frequency to the gas inlet, and by alternately switching between the process for applying AC power of the first frequency and the process for applying AC power of the second frequency, it is possible to obtain a silicon oxide film in which changes in stress value over time are suppressed, even without forming a modified layer.

[0008] That is, a silicon oxide film forming method according to a first aspect of the present invention comprises the steps of: introducing a process gas for forming a silicon oxide film onto a substrate to be processed in a process chamber from a gas inlet; applying AC power of a first frequency to the gas inlet; and applying AC power of a second frequency higher than the first frequency to the gas inlet, wherein the steps of applying AC power of the first frequency and applying AC power of the second frequency are: At intervals of 2 seconds or more and 100 seconds or less, Switch alternately.

[0009] In the silicon oxide film forming method according to the first aspect of the present invention, as described above, a step of applying AC power of a first frequency to the gas inlet and a step of applying AC power of a second frequency higher than the first frequency to the gas inlet are alternately performed. This allows for the formation of a silicon oxide film in which changes in stress over time are suppressed. This point has been confirmed by experiments (examples) described below. As a result, a step of forming a modified layer is not required, thereby improving the production efficiency (throughput) of silicon oxide films in which changes in stress over time are suppressed. Furthermore, since it is not necessary to apply AC power of a relatively low frequency to the stage on which the substrate is placed, high-energy collision of the plasma-converted process gas with the substrate can be suppressed. As a result, defects in the substrate due to plasma collisions can be suppressed. This allows for the formation of a silicon oxide film in which changes in stress over time are suppressed without applying AC power to the substrate. Patent Document 1 describes the application of AC power to the substrate in order to attract ions in the plasma. However, in today's device environment, plasma damage has a negative effect on devices, and it is becoming increasingly difficult to apply AC power to the substrate to attract ions from the plasma as described above. Therefore, it is desirable to eliminate the change in stress value over time without applying AC power to the substrate (i.e., without causing plasma damage).

[0010] In the silicon oxide film forming method according to the first aspect, preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed a plurality of times, so that a total of four or more silicon oxide film layers can be formed by the steps of applying AC power of the first frequency and applying AC power of the second frequency, thereby stabilizing the film quality of the silicon oxide film.

[0011] In the silicon oxide film forming method according to the first aspect, preferably, of the steps of applying AC power of a first frequency and applying AC power of a second frequency, the step of applying AC power of the first frequency is performed first, and then the steps of applying AC power of the first frequency and applying AC power of the second frequency are performed alternately. With this configuration, the silicon oxide film layer is formed by first applying AC power of the first frequency, which is a relatively low frequency, so that a layer having compressive stress can be formed on the substrate first. This makes it easier for the silicon oxide film to adhere to the substrate.

[0012] In the silicon oxide film forming method according to the first aspect, the step of introducing the process gas from the gas inlet preferably includes introducing tetraethoxysilane (TEOS) gas, whereby the tetraethoxysilane (TEOS) gas is converted into plasma, and a silicon oxide film having a suppressed change in stress value over time can be easily formed on the substrate.

[0013] In the silicon oxide film forming method according to the first aspect, the stress value of the silicon oxide film to be formed is preferably adjusted by adjusting the ratio of the application time of the step of applying AC power of the first frequency to the step of applying AC power of the second frequency, whereby a silicon oxide film having a desired stress value and suppressed change in the stress value over time can be formed on the substrate.

[0014] In order to achieve the above object, a silicon oxide film forming apparatus according to a second aspect of the present invention includes a processing chamber in which a substrate to be processed is placed, a gas inlet that introduces a processing gas for forming a silicon oxide film on the substrate in the processing chamber, an AC power application unit that applies AC power to the gas inlet, and a control unit, wherein the control unit controls the introduction of the processing gas from the gas inlet and switches the AC power applied from the AC power application unit between AC power of a first frequency and AC power of a second frequency higher than the first frequency. , at intervals of 2 seconds or more and 100 seconds or less, Control is performed to switch between them alternately.

[0015] In the silicon oxide film forming apparatus according to the second aspect of the present invention, as described above, the control unit alternately switches the AC power applied from the AC power application unit to the gas inlet between AC power of a first frequency and AC power of a second frequency higher than the first frequency. This allows a silicon oxide film to be formed with reduced change in stress over time. This has been confirmed by experiments (examples) described below. As a result, a modified layer formation step is not required, and a silicon oxide film forming apparatus can be provided that can improve the production efficiency (throughput) of a silicon oxide film with reduced change in stress over time. Furthermore, because a relatively low-frequency AC power is not applied to the stage on which the substrate is placed, high-energy collision of the plasma-converted process gas with the substrate can be suppressed. As a result, defects in the substrate caused by plasma collision can be suppressed. [Effects of the Invention]

[0018] According to the present invention, as described above, it is possible to improve the production efficiency of silicon oxide films in which the change in stress value over time is suppressed. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a substrate processing apparatus. [Figure 2] FIG. 1 is a flow chart for explaining a method for forming a silicon oxide film. [Figure 3]1 is a schematic diagram showing a silicon oxide film formed by a silicon oxide film forming method. [Figure 4] 10 is a graph showing film stress versus time ratio of low frequency and high frequency when AC power applied to the upper portion is alternately switched between low frequency and high frequency according to an embodiment. [Figure 5] 10 is a graph showing an etching rate versus a time ratio of a low frequency and a high frequency when AC power applied to an upper portion is alternately switched between a low frequency and a high frequency according to an embodiment. [Figure 6] 10 is a graph showing film stress versus high frequency power when AC power applied to the upper portion according to Comparative Example 1 is at a high frequency. [Figure 7] 10 is a graph showing an etching rate versus high frequency power when AC power applied to the upper portion is set to a high frequency in Comparative Example 1. [Figure 8] 10 is a graph showing film stress versus low-frequency power when AC power applied to the upper portion according to Comparative Example 2 is set to a low frequency. [Figure 9] 10 is a graph showing the etching rate versus the power of low-frequency power when AC power applied to the upper portion is set to a low frequency in Comparative Example 2. [Figure 10] 10 is a graph showing film stress versus low-frequency power applied to the lower portion when AC power applied to the upper portion is high frequency and AC power applied to the lower portion is low frequency according to Comparative Example 3. [Figure 11] 10 is a graph showing the etching rate versus the low-frequency power of the lower portion when AC power applied to the upper portion is of a high frequency and AC power applied to the lower portion is of a low frequency according to Comparative Example 3. [Figure 12] 10 is a graph showing film stress versus high frequency power applied to the upper portion when AC power applied to the upper portion is of a high frequency and AC power applied to the lower portion is of a low frequency according to Comparative Example 4. [Figure 13]10 is a graph showing the etching rate versus the power of high frequency power in the upper part when AC power applied to the upper part is of a high frequency and AC power applied to the lower part is of a low frequency according to Comparative Example 4. [Figure 14] 1 is a graph showing film stress versus etching rate immediately after film formation in accordance with an example and a comparative example. [Figure 15] 1 is a graph showing film stress versus etching rate after aging (after time has passed) in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] A substrate processing apparatus 100 for performing a substrate processing method according to this embodiment will be described with reference to FIG.

[0022] (Substrate processing equipment) As shown in Fig. 1, the substrate processing apparatus 100 is a parallel-plate plasma processing apparatus that generates plasma in a processing chamber 10 and forms a film on a substrate 200. In other words, the substrate processing apparatus 100 is a parallel-plate plasma CVD apparatus. The substrate 200 is formed from a material such as silicon, quartz glass, borosilicate glass, silicon carbide, gallium arsenide, or sapphire. The substrate processing apparatus 100 is an example of a "silicon oxide film forming apparatus" in the claims.

[0023] The substrate processing apparatus 100 includes a processing chamber 10, a substrate placement unit 20, a gas supply unit 30, an AC power supply unit 40, an exhaust unit 50, a heater 60, and a control unit .

[0024] The processing chamber 10 has a closed space covered by a housing 11, and accommodates a substrate placement part 20 in the closed space of the housing 11. In the processing chamber 10, a substrate 200 to be processed is placed.

[0025] The substrate mounting portion 20 includes a stage 21 on which the substrate 200 is mounted. The stage 21 is provided so as to be able to move up and down freely within the processing chamber 10 by an elevation cylinder 22.

[0026] The gas supply device 30 supplies process gases for processing the substrate 200 to the process chamber 10. The gas supply device 30 supplies process gases for forming a silicon oxide film 210 (see FIG. 3) in the process chamber 10. Specifically, the gas supply device 30 includes an O gas supply unit 31 for supplying oxygen (O) gas, a TEOS gas supply unit 32 for supplying tetraethoxysilane (TEOS) gas, and a rare gas supply unit 33 for supplying a rare gas (helium or argon). The process gases supplied from the gas supply units are introduced into the process chamber 10 from a gas introduction unit 35 provided in the process chamber 10 via a branched gas supply pipe 34. That is, the gas introduction unit 35 introduces the process gas for forming the silicon oxide film 210 onto the substrate 200 in the process chamber 10. The gas introduction unit 35 is a shower head gas introduction unit.

[0027] The AC power supply device 40 supplies AC power to the processing chamber 10. The AC power supply device 40 includes a low-frequency power application unit 41 and a high-frequency power application unit 42 that supply AC power to the upper electrode (gas inlet unit 35) to generate plasma from the processing gas in the processing chamber 10. The AC power supply device 40 also includes a lower AC power application unit 43 that supplies AC power to the lower electrode (stage 21) to supply AC power for the bias potential. The AC power supply device 40 also includes a switching unit 44 that switches the AC power supplied to the upper electrode (gas inlet unit 35) between the low-frequency power application unit 41 and the high-frequency power application unit 42. The low-frequency power application unit 41 and the high-frequency power application unit 42 are examples of the "AC power application unit" in the claims.

[0028] The low-frequency power application unit 41 and the high-frequency power application unit 42, which supply AC power to the upper electrode, apply AC power to the gas introduction unit 35. The low-frequency power application unit 41 supplies AC power at a relatively low frequency. For example, the low-frequency power application unit 41 supplies AC power at a frequency of several Hz to several hundred kHz. The low-frequency power application unit 41 also supplies AC power with a power of 10 W or more and 500 W or less. The high-frequency power application unit 42 supplies AC power at a relatively high frequency. For example, the high-frequency power application unit 42 supplies AC power with a frequency of several MHz to several tens of MHz. The high-frequency power application unit 42 also supplies AC power with a power of 10 W or more and 500 W or less.

[0029] The lower AC power application unit 43, which supplies AC power to the lower electrode, applies AC power to the stage 21 on which the substrate 200 is placed. The lower AC power application unit 43 supplies AC power at a relatively low frequency. For example, the lower AC power application unit 43 supplies AC power at a frequency of several kHz to several hundred kHz. The lower AC power application unit 43 also supplies AC power with a power of 10 W or more and 500 W or less.

[0030] Under the control of the control unit 70, the switching unit 44 switches the power supply device electrically connected to the gas introduction unit 35 between the low-frequency power application unit 41 and the high-frequency power application unit 42.

[0031] The exhaust system 50 reduces the pressure inside the processing chamber 10. The exhaust system 50 includes a vacuum pump 51 that exhausts gas inside the processing chamber 10, and an exhaust pipe 52 that connects the vacuum pump 51 to the inside of the processing chamber 10. The vacuum pump 51 exhausts gas inside the processing chamber 10 via the exhaust pipe 52, and the inside of the processing chamber 10 is set to a predetermined pressure state close to a vacuum.

[0032] The heater 60 heats the processing chamber 10. Specifically, the heater 60 includes a heater 61 that heats the substrate 200 and a heater 62 that heats the gas inlet 35. The heater 61 heats the stage 21 to about 200°C, for example. The heater 62 heats the gas inlet 35 to about 200°C, for example.

[0033] The control unit 70 controls each part of the substrate processing apparatus 100. Specifically, the control unit 70 controls the gas supply unit 30 and the AC power supply unit 40 to control the process of forming the silicon oxide film 210 on the substrate 200.

[0034] (Silicon oxide film formation method) Next, an outline of the silicon oxide film forming method of this embodiment will be described.

[0035] The silicon oxide film formation method of this embodiment includes the steps of introducing a process gas for forming a silicon oxide film 210 onto a substrate 200 to be processed in a process chamber 10 from a gas inlet 35, applying AC power of a first frequency (low frequency) to the gas inlet 35, and applying AC power of a second frequency (high frequency) higher than the first frequency to the gas inlet 35. In the silicon oxide film formation method of this embodiment, the step of applying AC power of the first frequency (low frequency) and the step of applying AC power of the second frequency (high frequency) are alternately performed.

[0036] The silicon oxide film forming method of this embodiment is performed by a process in the substrate processing apparatus 100. That is, to perform the silicon oxide film forming method, the control unit 70 of the substrate processing apparatus 100 controls the introduction of a process gas from the gas inlet unit 35 and controls the alternating current power applied from the low-frequency power application unit 41 and the high-frequency power application unit 42 to alternate between an AC power of a first frequency (low frequency) and an AC power of a second frequency (high frequency) that is higher than the first frequency.

[0037] In the step of applying AC power of a first frequency to gas introduction portion 35, AC power of a frequency of several kHz to several hundred kHz is supplied from low frequency power application portion 41, and AC power of the first frequency (low frequency) is applied to gas introduction portion 35. In the step of applying AC power of a second frequency to gas introduction portion 35, AC power of a frequency of several MHz to several tens of MHz is supplied from high frequency power application portion 42, and AC power of the second frequency (high frequency) is applied to gas introduction portion 35.

[0038] In addition, in the process of alternately switching between the process of applying AC power of a first frequency (low frequency) and the process of applying AC power of a second frequency (high frequency), the control unit 70 controls the switching unit 44 to alternately switch the power supply device electrically connected to the gas introduction unit 35 between the low-frequency power application unit 41 and the high-frequency power application unit 42.

[0039] In the silicon oxide film forming method of this embodiment, the step of applying AC power of a first frequency (low frequency) and the step of applying AC power of a second frequency (high frequency) are alternately performed multiple times (two or more times). Preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed 10 or more times each. More preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed 15 or more times each. Also, preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed 30 or less times each. More preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed 20 or less times each.

[0040] In the silicon oxide film formation method of this embodiment, the process of applying AC power of a first frequency (low frequency) and the process of applying AC power of a second frequency (high frequency) are alternately switched at intervals of 1 second to 100 seconds, preferably 2 seconds to 100 seconds. By setting the switching interval to 2 seconds or more, it is possible to suppress the effects of fluctuations such as plasma instability and plasma fluctuations (for example, reflected waves occurring when the set effective power is not applied) when plasma is ignited.

[0041] In the silicon oxide film forming method of this embodiment, the stress value of the silicon oxide film 210 to be formed is adjusted by adjusting the ratio of the application time between the step of applying AC power of the first frequency and the step of applying AC power of the second frequency. That is, the stress value of the silicon oxide film 210 is adjusted by adjusting the application time of AC power of the first frequency (low frequency) and the application time of AC power of the second frequency (high frequency). Specifically, the stress value of the silicon oxide film 210 is reduced by increasing the ratio of the application time of AC power of the first frequency (low frequency) to the total application time (reducing the ratio of the application time of AC power of the second frequency (high frequency) to the total application time). On the other hand, the stress value of the silicon oxide film 210 is increased by decreasing the ratio of the application time of AC power of the first frequency (low frequency) to the total application time (reducing the ratio of the application time of AC power of the second frequency (high frequency) to the total application time).

[0042] Here, when the stress value of the silicon oxide film 210 is tensile stress, which is stress in the direction in which the film contracts, the sign of the value is plus (+), and the greater the degree of tension, the greater the value. On the other hand, when the stress value of the silicon oxide film 210 is compressive stress, which is stress in the direction in which the film expands, the sign of the value is minus (-), and the greater the degree of compression, the smaller the value.

[0043] Furthermore, in the silicon oxide film formation method of this embodiment, of the steps of applying AC power of a first frequency (low frequency) and applying AC power of a second frequency (high frequency), the step of applying AC power of the first frequency (low frequency) is performed first, and then the steps of applying AC power of the first frequency (low frequency) and applying AC power of the second frequency (high frequency) are alternately performed.

[0044] In the silicon oxide film forming method of this embodiment, in the step of introducing the processing gas from the gas inlet 35, tetraethoxysilane (TEOS) gas is introduced.

[0045] 2, in the silicon oxide film forming method of this embodiment, in step S1, a process gas for forming a silicon oxide film 210 is introduced into the process chamber 10 heated by the heaters 61 and 62. In step S2, AC power of a first frequency (low frequency) is applied to the gas inlet 35 for a first predetermined time. As a result, a first layer 211 (FIG. 3) is deposited on the substrate 200.

[0046] In step S3, AC power of a second frequency (high frequency) is applied to the gas inlet 35 for a second predetermined time. As a result, a second layer 212 (FIG. 3) is deposited on the substrate 200. In addition, in steps S2 to S3, the AC power applied to the gas inlet 35 is switched from a first frequency (low frequency) to a second frequency (high frequency). The first predetermined time during which AC power of the first frequency (low frequency) is applied and the second predetermined time during which AC power of the second frequency (high frequency) is applied are each set based on a target stress value of the silicon oxide film 210 to be formed.

[0047] In step S4, it is determined whether the application of AC power at the first frequency (low frequency) and the application of AC power at the second frequency (high frequency) have been switched a set number of times. If the switching has been completed the set number of times, the process returns to step S5. If the set number of times has not been reached, the process returns to step S2. In this case, the AC power applied to the gas introduction part 35 is switched from the second frequency (high frequency) to the first frequency (low frequency). Then, the processes of steps S2 to S4 are repeated until the set number of times is reached.

[0048] 3, the silicon oxide film 210 formed by the silicon oxide film forming method of this embodiment includes a first layer 211 formed by a process of applying AC power of a first frequency (low frequency) and a second layer 212 formed by a process of applying AC power of a second frequency (high frequency). The first layers 211 and the second layers 212 are alternately stacked in multiple layers. In this embodiment, the change in film stress of the silicon oxide film 210 is 20 MPa or less one day and four days after the silicon oxide film 210 is formed.

[0049] That is, in this embodiment, the silicon oxide film 210 includes a first layer 211 having compressive stress and a second layer 212 having tensile stress. The first layers 211 and second layers 212 are alternately stacked in multiple layers. The multiple stacked first layers 211 and second layers 212 have a tensile film stress of +100 MPa or more, and the change in film stress is 20 MPa or less one day and four days after formation.

[0050] (Example) Next, an embodiment of the present invention will be described with reference to FIGS.

[0051] In the examples, a silicon oxide film 210 was formed on a substrate 200 using the substrate processing apparatus 100 according to the embodiment. In the examples, results were obtained regarding the change in stress value of the formed silicon oxide film over time. In the examples, results were obtained regarding the etching rate of the formed silicon oxide film. The environment in which the stress value of the formed silicon oxide film was measured and the environment in which the substrate was left to measure the change over time were an atmospheric environment at room temperature (23±2°C) and humidity of 30% to 60%. The environment in which the etching rate was measured was also room temperature (23±2°C).

[0052] The change in the stress value of the silicon oxide film over time was measured by measuring the stress value immediately after the silicon oxide film was formed (within 10 minutes after film formation) and the stress value after a predetermined time had elapsed since film formation. The stress value of the silicon oxide film was calculated based on the amount of warpage of the substrate 200 on which the silicon oxide film was formed. The stress value of the silicon oxide film was measured using a thin film stress measurement device (manufactured by Toho Technology Co., Ltd., model "FLX-2320-S").

[0053] The etching rate of the silicon oxide film was calculated by treating the formed silicon oxide film with a chemical solution (9:1 HF (hydrogen fluoride)) and measuring the amount of etching (film thickness) per unit time. Because the etching rate of the silicon oxide film depends on the treatment time and the concentration of the chemical solution, it was calculated as a ratio to that of a thermally oxidized film (TOX) treated at the same time. That is, the measured etching rate of the silicon oxide film was divided by the etching rate of the thermally oxidized film (TOX) to obtain the etching rate ratio. In other words, an etching rate ratio of 1 means that the etching rate of the silicon oxide film is equal to the etching rate of the thermally oxidized film (TOX). The thickness of the silicon oxide film used to calculate the etching rate was measured using a spectroscopic ellipsometer thin film material evaluation system (manufactured by Sentech, model "SENresarch 4.0").

[0054] In the example shown in Figures 4 and 5, the AC power applied to the upper gas inlet 35 was repeatedly switched between a first frequency (low frequency) and a second frequency (high frequency) to form a silicon oxide film on the substrate 200. The application time of the AC power of the first frequency (low frequency) and the application time of the AC power of the second frequency (high frequency) were also changed to form a silicon oxide film on the substrate 200. In the example shown in Figures 4 and 5, the lower electrode (stage 21) was grounded. The horizontal axis in each of the graphs in Figures 4 and 5 represents the percentage (%) of the application time of the AC power of the second frequency (high frequency) relative to the total application time (the sum of the application time of the AC power of the first frequency (low frequency) and the application time of the AC power of the second frequency (high frequency)).

[0055] 4 and 5, oxygen (O2) gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas was supplied at a flow rate of 15 sccm, and helium gas was supplied at a flow rate of 1000 sccm. Also, AC power of a first frequency (low frequency) was applied at a frequency of 380 kHz and a power of 200 W, and AC power of a second frequency (high frequency) was applied at a frequency of 13.56 MHz and a power of 25 W.

[0056] In the examples, it was found that the stress value of the silicon oxide film to be formed can be easily adjusted (controlled) by changing the ratio between the application time of AC power of the first frequency (low frequency) and the application time of AC power of the second frequency (high frequency), as shown in Figure 4. Furthermore, in the examples, it was found that by changing the ratio between the application time of AC power of the first frequency (low frequency) and the application time of AC power of the second frequency (high frequency), it is possible to adjust the film stress to tensile stress so that the stress value of the silicon oxide film becomes positive (+), and also to adjust the film stress to compressive stress so that the stress value of the silicon oxide film becomes negative (-).

[0057] 4, it was found that the stress value of the silicon oxide film did not change substantially after 1 day (after lapse of time) or 4 days (after lapse of time) compared to immediately after film formation (within 10 minutes after film formation). In other words, it was found that by alternately applying a first frequency (low frequency) AC power and a second frequency (high frequency) AC power, a silicon oxide film in which the change in stress value over time was suppressed could be obtained without forming a modified layer. Specifically, when the ratio (%) of the application time of the second frequency (high frequency) AC power to the total application time was between about 10% and about 95%, the change (decrease) in the film stress of the silicon oxide film after lapse of 1 day was less than 10 MPa. Furthermore, when the ratio (%) of the application time of the second frequency (high frequency) AC power to the total application time was between approximately 10% and approximately 95%, the change (decrease) in the film stress of the silicon oxide film after 4 days was less than 17 MPa (i.e., 20 MPa or less).

[0058] Furthermore, in the examples, as shown in FIG. 5, it was found that the etching rate of the formed silicon oxide film can be easily adjusted (controlled) by changing the ratio of the application time of AC power of the first frequency (low frequency) to the application time of AC power of the second frequency (high frequency). That is, it was found that the etching rate increases as the ratio of the application time of AC power of the second frequency (high frequency) increases. Furthermore, as shown in FIGS. 4 and 5, the silicon oxide film according to the examples shows a change (change over time) of 20 MPa or less after four days, and there is a correlation in which the etching rate increases as the film stress increases. In particular, as shown in FIGS. 4 and 5, the silicon oxide film according to the examples shows a change (change over time) of 20 MPa or less after four days, even when the film stress is a tensile stress of +100 MPa or more.

[0059] (Comparative Example 1) 6 and 7, only the second frequency (high frequency) AC power was applied to the upper gas inlet part 35, and a silicon oxide film was formed on the substrate 200. In addition, the power of the second frequency (high frequency) AC power applied to the upper gas inlet part 35 was changed to form a silicon oxide film on the substrate 200. The horizontal axis in each of the graphs in FIGS. 6 and 7 represents the power of the second frequency (high frequency) AC power applied to the upper gas inlet part 35.

[0060] 6 and 7, oxygen (O2) gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas was supplied at a flow rate of 15 sccm, and helium gas was supplied at a flow rate of 1000 sccm. Also, a second frequency (high frequency) AC power was applied at a frequency of 13.56 MHz.

[0061] In Comparative Example 1, as shown in FIG. 6, even when the power of the second frequency (high frequency) AC power applied to the upper gas inlet part 35 is changed, no correlation is found in the stress value of the silicon oxide film to be formed, and therefore it is difficult to adjust the stress value of the silicon oxide film to be formed.

[0062] 6, the stress value of the silicon oxide film in Comparative Example 1 significantly changes after three days have passed (after the passage of time) compared to immediately after film formation (within 10 minutes after film formation). Specifically, when only the second frequency (high frequency) AC power was applied to the upper gas inlet 35, the maximum change (decrease) in film stress of the silicon oxide film after three days was approximately 190 MPa. It can also be seen that, regardless of the power of the second frequency (high frequency) AC power applied to the upper gas inlet 35, the stress values ​​of the silicon oxide film immediately after film formation were all tensile stresses (positive stress values), and the stress values ​​of the silicon oxide film significantly changed over time (easily changed over time).

[0063] Furthermore, in Comparative Example 1, as shown in FIG. 7, even when the power of the second frequency (high frequency) AC power applied to the upper gas inlet part 35 is changed, no correlation is found in the etching rate of the silicon oxide film formed, making it difficult to adjust the etching rate of the silicon oxide film formed.

[0064] (Comparative Example 2) 8 and 9, only the first frequency (low frequency) AC power was applied to the upper gas inlet part 35, and a silicon oxide film was formed on the substrate 200. In addition, the power of the first frequency (low frequency) AC power applied to the upper gas inlet part 35 was changed to form a silicon oxide film on the substrate 200. The horizontal axis in each of the graphs in FIGS. 8 and 9 represents the power of the first frequency (low frequency) AC power applied to the upper gas inlet part 35.

[0065] 8 and 9, oxygen (O2) gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas was supplied at a flow rate of 15 sccm, and helium gas was supplied at a flow rate of 1000 sccm. Also, AC power of a first frequency (low frequency) was applied at a frequency of 380 kHz.

[0066] In Comparative Example 2, as shown in FIG. 8, even when the power of the AC power of the first frequency (low frequency) applied to the upper gas inlet part 35 is changed, no correlation is found in the stress value of the silicon oxide film to be formed, and therefore it is difficult to adjust the stress value of the silicon oxide film to be formed.

[0067] 8, it can be seen that the stress value of the silicon oxide film in Comparative Example 2 changes significantly after three days have passed (after the passage of time) compared to immediately after film formation (within 10 minutes after film formation). Specifically, when only the first frequency (low frequency) AC power was applied to the upper gas inlet 35, the maximum change (decrease) in the film stress of the silicon oxide film after three days was approximately 290 MPa. It can also be seen that when the stress value of the silicon oxide film immediately after film formation is approximately -100 MPa or higher (larger in the tensile direction than approximately -100 MPa), the change in the stress value of the silicon oxide film over time is large (it is prone to change over time).

[0068] 9, it was found that in Comparative Example 2, the etching rate of the silicon oxide film formed could be adjusted by changing the power of the AC power of the first frequency (low frequency) applied to the upper gas inlet part 35. In other words, it was found that the etching rate decreased as the power of the AC power of the first frequency (low frequency) applied to the upper gas inlet part 35 increased.

[0069] (Comparative Example 3) 10 and 11, AC power of the second frequency (high frequency) was applied to the upper gas inlet part 35, and low-frequency AC power was applied to the lower stage 21, to form a silicon oxide film on the substrate 200. Furthermore, the power of the low-frequency AC power applied to the lower stage 21 was changed to form a silicon oxide film on the substrate 200. The horizontal axis in each graph of FIGS. 10 and 11 represents the power of the low-frequency AC power applied to the lower stage 21.

[0070] 10 and 11, oxygen (O2) gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas was supplied at a flow rate of 15 sccm, and helium gas was supplied at a flow rate of 1000 sccm. Second-frequency (high-frequency) AC power was applied to the upper gas inlet 35 at a frequency of 13.56 MHz and a power of 25 W. Low-frequency AC power was applied to the lower stage 21 at a frequency of 380 kHz.

[0071] 10, it is difficult to adjust the stress value of the silicon oxide film formed because no correlation can be found between the stress value of the silicon oxide film formed and the power of the low-frequency AC power applied to the lower stage 21. However, when focusing only on the stress value of the silicon oxide film immediately after film formation, it was found that the stress value of the silicon oxide film decreases (shifts toward compressive stress) as the power of the low-frequency AC power applied to the lower stage 21 increases.

[0072] 10, the stress value of the silicon oxide film in Comparative Example 3 significantly changes after three days have passed (after the passage of time) compared to immediately after film formation (within 10 minutes after film formation). Specifically, when the AC power applied to the upper gas inlet 35 was the second frequency (high frequency) and a low frequency AC power was applied to the lower stage 21, the maximum change (decrease) in the film stress of the silicon oxide film after three days was approximately 260 MPa. Furthermore, it can be seen that when the stress value of the silicon oxide film immediately after film formation was approximately -100 MPa or higher (increased in tension from approximately -100 MPa), the change in the stress value of the silicon oxide film significantly changes over time (is prone to change over time).

[0073] 11, it was found that in Comparative Example 3, the etching rate of the silicon oxide film formed could be adjusted by changing the power of the low-frequency AC power applied to the lower stage 21. In other words, it was found that the etching rate decreased as the power of the low-frequency AC power applied to the lower stage 21 increased.

[0074] Comparative Example 4 12 and 13, AC power of the second frequency (high frequency) was applied to the upper gas inlet part 35, and AC power of a low frequency was applied to the lower stage 21, to form a silicon oxide film on the substrate 200. Furthermore, the power of the AC power of the second frequency (high frequency) applied to the upper gas inlet part 35 was changed to form a silicon oxide film on the substrate 200. The horizontal axis in each graph of FIGS. 12 and 13 represents the power of the AC power of the second frequency (high frequency) applied to the upper gas inlet part 35.

[0075] 12 and 13, oxygen (O2) gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas was supplied at a flow rate of 15 sccm, and helium gas was supplied at a flow rate of 1000 sccm. Second-frequency (high-frequency) AC power was applied to the upper gas inlet 35 at a frequency of 13.56 MHz. Low-frequency AC power was applied to the lower stage 21 at a frequency of 380 kHz and a power of 50 W.

[0076] 12, in Comparative Example 4, even when the power of the second frequency (high frequency) AC power applied to the upper gas inlet part 35 is changed, no correlation is found in the stress value of the silicon oxide film formed, making it difficult to adjust the stress value of the silicon oxide film formed. However, when focusing only on the stress value of the silicon oxide film immediately after film formation, it was found that in an environment where low frequency AC power is applied to the lower stage 21, the stress value of the silicon oxide film decreases (shifts toward compressive stress) as the power of the AC power applied to the upper gas inlet part 35 increases.

[0077] 12, it can be seen that the stress value of the silicon oxide film in Comparative Example 4 changes significantly after three days have passed (after the passage of time) compared to immediately after film formation (within 10 minutes after film formation). Specifically, when the AC power applied to the upper gas inlet 35 was the second frequency (high frequency) and a low frequency AC power was applied to the lower stage 21, the maximum change (decrease) in the film stress of the silicon oxide film after three days was approximately 240 MPa. It can also be seen that when the stress value of the silicon oxide film immediately after film formation is approximately -50 MPa or higher (increasing in tension from approximately -50 Pa), the change in the stress value of the silicon oxide film over time is large (it is prone to change over time).

[0078] 13, it was found that in Comparative Example 4, the etching rate of the silicon oxide film formed could be adjusted by changing the power of the second frequency (high frequency) AC power applied to the upper gas inlet part 35. In other words, it was found that the etching rate decreased as the power of the second frequency (high frequency) AC power applied to the upper gas inlet part 35 increased.

[0079] (Relationship between etching rate and film stress) As shown in FIG. 14, the relationship between the etching rate and the film stress shows a correlation in that the greater the film stress immediately after film formation, the greater the etching rate in the Example, Comparative Example 2, Comparative Example 3, and Comparative Example 4. As shown in FIG. 15, the relationship between the etching rate and the film stress shows a correlation in that the greater the film stress after aging (after the passage of time) in the Example. Furthermore, comparing FIG. 14 and FIG. 15, it was found that when the stress value of the silicon oxide film immediately after film formation is above a certain level (for example, a stress greater on the tensile side than approximately -100 MPa to -50 MPa (low stress region)), or when the etching rate is above a certain level, the stress value of the silicon oxide film in Comparative Examples 1 to 4 changes significantly over time. In other words, under the processing conditions (upper high frequency application, upper low frequency application, upper high frequency application, and lower low frequency application) of Comparative Examples 1 to 4, it was found that it is difficult to suppress the change in stress value over time for silicon oxide films with low stress values ​​(generally -100 MPa to +100 MPa). Furthermore, as shown in FIGS. 14 and 15, the silicon oxide film according to the example shows a change (change over time) of 20 MPa or less after 4 days, and there is a correlation in which the etching rate increases as the film stress increases.

[0080] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0081] In the silicon oxide film forming method of this embodiment, as described above, the process of applying AC power of a first frequency to the gas inlet 35 and the process of applying AC power of a second frequency higher than the first frequency to the gas inlet 35 are alternately performed. This allows for the formation of a silicon oxide film in which changes in stress value over time are suppressed. As a result, a process of forming a modified layer is not required, thereby improving the production efficiency (throughput) of silicon oxide films in which changes in stress value over time are suppressed. Furthermore, because AC power of a relatively low frequency is not applied to the stage 21 on which the substrate 200 is placed, it is possible to suppress collision of the plasma-converted process gas with the substrate 200 due to high energy. As a result, it is possible to suppress defects in the substrate 200 caused by plasma collision.

[0082] In this embodiment, as described above, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed multiple times, thereby making it possible to form a total of four or more silicon oxide film layers by the steps of applying AC power of the first frequency and applying AC power of the second frequency, thereby stabilizing the film quality of the silicon oxide film.

[0083] Furthermore, in this embodiment, as described above, of the steps of applying AC power of a first frequency and applying AC power of a second frequency, the step of applying AC power of the first frequency is performed first, and then the steps of applying AC power of the first frequency and applying AC power of the second frequency are alternately performed. As a result, the silicon oxide layer is formed by first applying AC power of the first frequency, which is a relatively low frequency, so that a layer having compressive stress can be formed on the substrate 200 first. This makes it easier for the silicon oxide film to adhere to the substrate 200.

[0084] In this embodiment, as described above, tetraethoxysilane (TEOS) gas is introduced in the step of introducing the processing gas from the gas inlet 35. This converts the tetraethoxysilane (TEOS) gas into plasma, making it possible to easily form a silicon oxide film on the substrate 200 in which the change in stress value over time is suppressed.

[0085] In this embodiment, the stress value of the silicon oxide film to be formed is adjusted by adjusting the ratio of the application time of the step of applying AC power of the first frequency to the step of applying AC power of the second frequency, as described above, so that a silicon oxide film having a desired stress value and suppressed change in the stress value over time can be formed on the substrate 200.

[0086] (Variation) The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the above description of the embodiments, and further includes all modifications (variations) within the meaning and scope of the claims.

[0087] For example, in the above embodiment, an example was shown in which the silicon oxide film forming method was carried out using the substrate processing apparatus 100 shown in Figure 1 as the silicon oxide film forming apparatus, but the present invention is not limited to this. The apparatus configuration of the substrate processing apparatus (silicon oxide film forming apparatus) that carries out the silicon oxide film forming method of the present invention is not particularly limited, and may be different from the apparatus configuration shown in Figure 1.

[0088] In addition, in the above embodiment, an example of a configuration in which the gas inlet for introducing the process gas is disposed above the substrate and the substrate is disposed below is shown, but the present invention is not limited to this. In the present invention, the gas inlet for introducing the process gas may be disposed below the substrate and the substrate may be disposed above. In other words, the gas inlet to which AC power of a first frequency (low frequency) and AC power of a second frequency (high frequency) are alternately applied may be disposed below the substrate.

[0089] Furthermore, in the above embodiment, an example of a configuration in which the step of applying AC power of the first frequency (low frequency) is performed first among the steps of applying AC power of the first frequency (low frequency) and applying AC power of the second frequency (high frequency) has been described. However, the present invention is not limited to this. In the present invention, the step of applying AC power of the second frequency (high frequency) among the steps of applying AC power of the first frequency (low frequency) and applying AC power of the second frequency (high frequency) may be performed first. In particular, when plasma damage due to direct exposure of the substrate surface to plasma is a concern, it is preferable to apply AC power of the second frequency (high frequency) first. When the frequency of AC power applied to the gas inlet is high, the potential of the gas inlet changes faster than at low frequencies, and electrons move toward the substrate. However, because ions have a much larger mass than electrons, ions in the plasma cannot follow the potential change of the gas inlet and have difficulty moving toward the substrate. Therefore, even if the substrate surface is directly exposed to plasma, high frequencies cause less plasma damage than low frequencies.

[0090] Furthermore, in the above embodiment, an example of a configuration in which the same number of steps of applying AC power of a first frequency (low frequency) and the same number of steps of applying AC power of a second frequency (high frequency) are performed has been shown, but the present invention is not limited to this. In the present invention, one of the steps of applying AC power of a first frequency (low frequency) and the step of applying AC power of a second frequency (high frequency) may be performed a greater number of times (for example, 1) than the other. In other words, AC power of the first frequency (low frequency) may be applied first, and then the steps of applying AC power of the first frequency (low frequency) and the step of applying AC power of a second frequency (high frequency) may be alternately performed, and finally, AC power of the first frequency (low frequency) may be applied to terminate the process. Alternatively, AC power of the second frequency (high frequency) may be applied first, and then a process of applying AC power of the first frequency (low frequency) and a process of applying AC power of the second frequency (high frequency) may be alternately performed, and finally AC power of the second frequency (high frequency) may be applied to terminate the process.

[0091] In the above embodiment, an example of a configuration in which a silicon oxide film is formed using tetraethoxysilane (TEOS) gas has been shown, but the present invention is not limited to this. In the present invention, a silicon oxide film may be formed using silane (SiH4) gas and nitrous oxide (NO) gas by alternately switching between a process of applying AC power of a first frequency (low frequency) to the gas inlet and a process of applying AC power of a second frequency (high frequency) to the gas inlet.

[0092] [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0093] (Item 1) introducing a processing gas for forming a silicon oxide film onto a substrate to be processed in a processing chamber from a gas inlet; applying AC power of a first frequency to the gas inlet; applying AC power of a second frequency higher than the first frequency to the gas inlet, A silicon oxide film forming method, wherein the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed.

[0094] (Item 2) 2. The silicon oxide film forming method according to item 1, wherein the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched so as to be performed multiple times each.

[0095] (Item 3) 3. The method for forming a silicon oxide film according to item 1 or 2, wherein, of the step of applying AC power of the first frequency and the step of applying AC power of the second frequency, the step of applying AC power of the first frequency is performed first, and thereafter, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed.

[0096] (Item 4) 4. The method for forming a silicon oxide film according to any one of items 1 to 3, wherein in the step of introducing the processing gas from the gas inlet, tetraethoxysilane (TEOS) gas is introduced.

[0097] (Item 5) 5. The silicon oxide film forming method according to any one of items 1 to 4, wherein a stress value of the silicon oxide film to be formed is adjusted by adjusting a ratio of an application time of the step of applying AC power of the first frequency and an application time of the step of applying AC power of the second frequency.

[0098] (Item 6) a processing chamber in which a substrate to be processed is placed; a gas inlet for introducing a processing gas for forming a silicon oxide film onto the substrate in the processing chamber; an AC power application unit that applies AC power to the gas introduction unit; a control unit, the control unit controls the introduction of the process gas from the gas introduction unit and alternately switches the AC power applied from the AC power application unit between AC power of a first frequency and AC power of a second frequency higher than the first frequency in the silicon oxide film forming apparatus.

[0099] (Item 7) a first layer having a compressive stress; a second layer having a tensile stress; The first layers and the second layers are alternately stacked in multiple layers, A silicon oxide film having a tensile film stress of +100 MPa or more when the first layer and the second layer are stacked in multiple layers, and a change in film stress of 20 MPa or less after one day has passed since the film was formed. [Explanation of symbols]

[0100] 10: processing chamber, 35: gas introduction section, 41: low frequency power application section (AC power application section), 42: high frequency power application section (AC power application section), 70: control section, 100: substrate processing apparatus (silicon oxide film forming apparatus), 200: substrate, 210: silicon oxide film, 211: first layer, 212: second layer

Claims

1. introducing a processing gas for forming a silicon oxide film onto a substrate to be processed in a processing chamber from a gas inlet; applying AC power of a first frequency to the gas inlet; applying AC power of a second frequency higher than the first frequency to the gas inlet, a step of applying AC power of the first frequency and a step of applying AC power of the second frequency, the steps being alternately performed at intervals of 2 seconds or more and 100 seconds or less;

2. 2. The method of forming a silicon oxide film according to claim 1, wherein the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched so as to be performed a plurality of times each.

3. 2. The method for forming a silicon oxide film according to claim 1, wherein, of the steps of applying AC power of the first frequency and applying AC power of the second frequency, the step of applying AC power of the first frequency is performed first, and thereafter, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately performed.

4. 2. The silicon oxide film forming method according to claim 1, wherein the step of introducing the process gas from the gas inlet portion introduces tetraethoxysilane (TEOS) gas.

5. 2. The silicon oxide film forming method according to claim 1, wherein a stress value of the silicon oxide film to be formed is adjusted by adjusting a ratio of an application time of the step of applying AC power of the first frequency to that of applying AC power of the second frequency.

6. a processing chamber in which a substrate to be processed is placed; a gas inlet for introducing a processing gas for forming a silicon oxide film onto the substrate in the processing chamber; an AC power application unit that applies AC power to the gas introduction unit; a control unit, the control unit controls the introduction of the process gas from the gas inlet unit and alternately switches the AC power applied from the AC power application unit between AC power of a first frequency and AC power of a second frequency higher than the first frequency, at intervals of 2 seconds to 100 seconds.

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