Apparatus and method for depositing a carbon-containing film on a substrate

Abstract

To provide a technique for depositing a carbon-containing film of good quality using high-frequency power of a VHF band or a UHF band.SOLUTION: An apparatus for depositing a carbon-containing film on a substrate includes a table which composes a lower electrode and on which the substrate is put and a gas shower head which is installed for supplying a film deposition gas of the carbon-containing film and connected to a high-frequency power source to supply high-frequency power of a VHF band or a UHF band to compose an upper electrode. The gap distance between the table and the gas shower head is set to be one or more times and four or less times the skin depth of the plasma of the film deposition gas formed by supplying the film deposition gas from the gas shower head into the treatment vessel and supplying the high-frequency power from the high-frequency power source to the upper electrode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates to an apparatus and method for depositing a carbon-containing film on a substrate. [Background technology]

[0002] In the manufacturing process of semiconductor devices, a hard mask is sometimes used to cover areas that are not removed by etching when patterning a film formed on a semiconductor wafer (hereinafter also referred to as "wafer"), which is the substrate. The applicant is considering using a diamond-like carbon (DLC) film, which is a carbon-containing film, as this hard mask.

[0003] For example, Patent Document 1 describes a technique for depositing diamond by heating a substrate in a gas plasma containing hydrogen gas using microwaves of 300 MHz or higher, supplying hydrocarbons to the substrate to decompose them, and depositing diamond. Patent Document 2 describes a technique for adjusting the hardness of a carbon film by changing the DC voltage (bias voltage) applied to the film deposition substrate electrode when forming a hard carbon film by plasma CVD. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 61-3320 [Patent Document 2] Japanese Patent Application Publication No. 4-41672 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] This disclosure provides a technology for depositing high-quality carbon-containing films using high-frequency power in the VHF or UHF band. [Means for solving the problem]

[0006] This disclosure relates to an apparatus for forming a carbon-containing film on a substrate, A mounting platform is provided inside the processing container on which the substrate is placed and which constitutes the lower electrode, The upper electrode comprises a gas shower head positioned in the processing container opposite the aforementioned stand, provided for supplying the carbon-containing film-forming gas into the processing container, and connected to a high-frequency power supply that supplies high-frequency power in the VHF or UHF band, The apparatus is configured such that the gap distance between the mounting base and the gas shower head is set to a distance within the range of 1 to 4 times the surface depth of the plasma of the film-forming gas, which is formed by supplying the film-forming gas from the gas shower head into the processing container and supplying high-frequency power from the high-frequency power supply to the upper electrode. [Effects of the Invention]

[0007] According to this disclosure, a high-quality carbon-containing film can be formed using high-frequency power in the VHF or UHF band. [Brief explanation of the drawing]

[0008] [Figure 1] This is an example of the configuration of a film deposition apparatus related to this disclosure. [Figure 2] This is a schematic diagram of a parallel-plate type plasma processing device. [Figure 3] This is an ion energy distribution diagram of a plasma formed by varying the bias high-frequency power. [Figure 4] This is a Raman spectral diagram of a DLC film formed using the aforementioned plasma. [Figure 5] This graph shows the changes in film stress and dry etching rate of the DLC film. [Figure 6A] This is the first ion energy distribution diagram of a plasma formed without supplying biasing high-frequency power. [Figure 6B] This is a second ion energy distribution diagram of a plasma formed without supplying biasing high-frequency power. [Figure 6C]It is a third ion energy distribution diagram of plasma formed without supplying high-frequency power for bias. [Figure 7A] It is a first Raman spectrum diagram of a DLC film formed using the plasma. [Figure 7B] It is a second Raman spectrum diagram of a DLC film formed using the plasma. [Figure 7C] It is a third Raman spectrum diagram of a DLC film formed using the plasma. [Figure 8] It is a first graph showing the relationship between plasma supply power and the film stress of the DLC film. [Figure 9] It is a second graph showing the relationship between plasma supply power and the film stress of the DLC film. [Figure 10] It is a first graph showing the relationship between plasma supply power and the film density of the DLC film. [Figure 11] It is a second graph showing the relationship between plasma supply power and the film density of the DLC film. [Figure 12] It is a first graph showing the relationship between plasma supply power and the film formation rate of the DLC film. [Figure 13] It is a second graph showing the relationship between plasma supply power and the film formation rate of the DLC film. [Figure 14] It is a graph showing the relationship between plasma supply power and plasma density. [Figure 15] It is a graph showing the relationship between plasma density and skin depth.

Embodiments for Carrying Out the Invention

[0009] <Film Forming Apparatus> First, referring to FIG. 1, a configuration example of a film forming apparatus 1 according to an embodiment for forming a DLC film, which is a carbon-containing film, on a wafer W will be described. FIG. 1 is a longitudinal side view of the film forming apparatus 1 in this example. This film forming apparatus 1 is configured as an apparatus for continuously supplying C2H2 gas, H2 gas, and Ar (argon) gas to the surface of the wafer W and forming a DLC film by plasma CVD method.

[0010] The film deposition apparatus 1 includes a grounded, substantially cylindrical processing container 10 made of aluminum or aluminum alloy. An inlet / outlet 11 is formed on the side of the processing container 10 for loading and unloading wafers W to and from a vacuum transport chamber (not shown). This inlet / outlet 11 is configured to be openable and closable by a gate valve 12. An exhaust passage 13 is connected to the bottom of the processing container 10. A vacuum exhaust section 14, including, for example, a pressure adjustment valve and a vacuum pump, is connected to the exhaust passage 13, and is configured to reduce the pressure inside the processing container 10 to a preset vacuum pressure. A DLC film deposition process is performed on the wafer W inside this processing container 10.

[0011] A mounting table 21 for holding wafers W in a nearly horizontal position is provided inside the processing container 10. The mounting table 21 is supported by a support column 22 that extends vertically inside the processing container 10. The lower side of the support column 22 penetrates the bottom plate of the processing container 10 and is connected to a lifting mechanism 23 provided on the lower side of the processing container 10. The lifting mechanism 23 has the function of raising and lowering the mounting table 21 inside the processing container 10. Around the support column 22 that protrudes downward from the processing container 10, a cover member 24 is provided between the processing container 10 and the lifting mechanism 23 to maintain airtightness inside the processing container 10.

[0012] A heater 25 is embedded in the mounting base 21, allowing the wafer W to be heated to a set temperature. In this example, the heating temperature of the wafer W is set to, for example, 100°C, within the range of 100 to 300°C. Furthermore, the processing container 10 is provided with lifting pins (not shown) for holding and raising / lowering the wafer W on the mounting table 21. By raising and lowering the lifting pins, the wafer W can be transferred between the mounting table 21 and an external transport mechanism (not shown).

[0013] In this example, the mounting platform 21 is grounded and constitutes the lower electrode for plasma formation of the DLC film deposition gas. Figure 1 shows an example of the lower electrode (mounting platform 21) without a bias high-frequency power supply connected to it. As shown in Figure 2 below, the mounting platform 21 may also be configured to have a bias high-frequency power supply 44 connected via a matching unit 43.

[0014] Furthermore, a flat, disc-shaped gas showerhead 3 for supplying film-forming gas to the wafer W is provided on the ceiling surface of the processing container 10. The gas showerhead 3 is attached to the processing container 10 via an insulating member 34. A diffusion space 31 for diffusing the film-forming gas is formed inside the gas shower head 3. Furthermore, numerous discharge holes 32 for discharging the film-forming gas toward the wafer W are dispersed on the bottom surface of the diffusion space 31.

[0015] One end of the power supply rod 33 is connected to the upper surface of the gas shower head 3 described above, and the other end is connected to the matching unit 41. In the example shown in Figure 1, the matching unit 41 is provided on the upper side of the cover member 35 that covers the upper surface of the processing container 10. The matching unit 41 is connected to a high-frequency power supply 42 that supplies high-frequency power for plasma formation. From this perspective, the gas shower head 3 constitutes the upper electrode for plasma formation of the film-forming gas.

[0016] As described above, the film deposition apparatus 1 of this disclosure comprises a parallel plate type plasma processing apparatus consisting of a gas shower head 3 forming the upper electrode and a mounting table 21 forming the lower electrode. A wafer W is placed in the space between the gas shower head 3 and the mounting table 21, and by supplying gases such as C2H2 and H2 and supplying high-frequency power, these gases are ionized and plasma is formed.

[0017] The high-frequency power supply 42 supplies high-frequency power at frequencies within the VHF band (30 MHz to 300 MHz) or the UHF band (300 MHz to 3 GHz). The following example describes a case where the power supply is configured to supply high-frequency power at 90 MHz or 180 MHz.

[0018] The downstream end of the gas supply channel 51 is connected to the diffusion space 31 of the gas showerhead 3. Upstream of this gas supply channel 51, the C2H2 gas supply pipe 52, which is a supply channel for C2H2 gas, the raw material for the DLC film, the H2 gas supply pipe 53, which is a supply channel for H2 gas, the reaction gas, and the Ar gas supply pipe 54, which is a supply channel for Ar gas added for plasma generation, converge.

[0019] A C2H2 gas supply source 501 is connected to the upstream end of the C2H2 gas supply pipe 52, and a flow rate control unit M501 and a valve V501 are installed in that order from the upstream side. Similarly, an H2 gas supply source 502 is connected to the upstream end of the H2 gas supply pipe 53, and a flow rate control unit M502 and a valve V502 are installed in that order from the upstream side. Furthermore, an Ar gas supply source 503 is connected to the upstream end of the Ar gas supply pipe 54, and a flow rate control unit M503 and a valve V503 are installed in that order from the upstream side. These mixed gases of C2H2 gas, H2 gas, and Ar gas flow into the diffusion space 31 of the gas showerhead 3 via the gas supply passage 51, and are supplied into the processing container 10 as a film-forming gas through the discharge hole 32.

[0020] The film deposition apparatus 1, having the configuration described above, includes a control unit 100. The control unit 100 is composed of a computer including a storage unit for storing a program, memory, and a CPU. The program is structured with instructions (steps) to execute the DLC film deposition process by outputting control signals from the control unit 100 to each part of the film deposition apparatus 1, and controlling the supply and disconnection of each gas and the supply of high-frequency power. The program is stored in the computer's storage unit, such as a flexible disk, compact disk, hard disk, MO (magneto-optical disk), or non-volatile memory, and is read from this storage unit and installed in the control unit 100.

[0021] <Film deposition process> Let me briefly explain the operation of the film deposition apparatus 1, which has the configuration described above. First, the gate valve 12 is opened, and the wafer W is loaded through the loading port 11 by a transport mechanism located in a vacuum transport chamber (not shown). The loaded wafer W is then transferred from the transport mechanism to the mounting table 21 via a lifting pin (not shown) and placed on its upper surface (the process of placing the wafer W on the mounting table 21). Next, the transport mechanism is moved out of the processing container 10, and the gate valve 12 is closed. Then, the processing container 10 is evacuated by the vacuum exhaust unit 14, and the pressure inside the processing container 10 is adjusted to a preset pressure. The wafer W is also heated to 100°C as described above by the heater 25.

[0022] Subsequently, the supply of film-forming gas is started, and the supply of high-frequency power from the high-frequency power supply 42 is also started. In addition, as shown in the example in Figure 2, the mounting base 21 is connected High-frequency power supply for bias 44 If high-frequency power is to be supplied for biasing, this power supply will also be started. Through the operations described above, the film-forming gas supplied into the processing container 10 is converted into plasma, and a DLC film is formed on the surface of the wafer W by the ions contained in the plasma (a process of forming a carbon-containing film on a substrate).

[0023] By continuously forming a film with the plasma-formed film-forming gas for the preset period in this way, a DLC film with a desired film thickness is formed. Next, the supply of the high-frequency power is terminated and the supply of the film-forming gas is stopped. Then, the wafer W is unloaded from the processing container 10 in the reverse procedure to the loading procedure and waits for the loading of the next wafer W.

[0024] <Film quality control of DLC film> When forming a DLC film using the film-forming apparatus 1 having the configuration described above, from the viewpoint of production efficiency, it is preferable to be able to perform a film-forming process with a higher film-forming speed. From this viewpoint, the inventors focused on high-frequency power in the VHF band or UHF band as a frequency range in which a plasma density higher than the conventionally used frequency (13.56 MHz) can be obtained.

[0025] Also, when used for the purpose of a hard mask, the DLC film preferably has high etching selectivity. From this viewpoint, the film density is an index for evaluating the etching selectivity of the DLC film. That is, a DLC film with a high film density has a low impurity content and a bonding state close to diamond, so it tends to have high etching resistance. When the film density is 1.8 g / cm 3 Above, preferably, 2.0 g / cm 3 Above, it can be evaluated that the DLC film exhibits sufficiently high etching resistance in practical use.

[0026] Based on such problems, the inventors explored film-forming conditions under which a DLC film with good film quality can be obtained with high productivity. As a result, it was found that there is not a simple correspondence relationship that a high-density DLC film can be obtained at a high film-forming speed by supplying high-frequency power in the VHF band or UHF band at a high output to plasmaize the film-forming gas. In order to find such film-forming conditions, it is necessary to select appropriate control variables based on a sufficient understanding of the film-forming mechanism of the DLC film and the characteristics of the plasma that change according to the supply method of the high-frequency power, and then specify a suitable control range.

[0027] The inventors understand that in the formation of a DLC film with a high film density, ions in the plasma of the film-forming gas are important. That is, by supplying ions of the film-forming gas having an appropriate ion energy at a high density, the film density of the DLC film can also be increased. On the other hand, the radical component contained in the plasma is a factor that reduces the film density of the DLC film.

[0028] Based on such findings, DLC film formation was performed using a film-forming apparatus 1 having substantially the same configuration as that described using FIG. 1, and the film-forming conditions were changed to measure the distribution of ion energy in the plasma and the characteristics of the DLC film. FIG. 2 schematically shows the film-forming apparatus 1 (parallel plate type plasma processing apparatus) of FIG. 1. As the film-forming conditions, (i) the supply power from the high-frequency power supply 42, (ii) the presence or absence of supply of high-frequency power for bias, (iii) when supplying high-frequency power for bias, the supply power thereof, and (iv) the gap distance between the mounting table 21 and the gas shower head 3 (hereinafter, also referred to as “electrode gap”) were changed. The electrode gap can be adjusted by raising and lowering the mounting table 21.

[0029] Also, as an index for evaluating the influence of the electrode gap, attention was paid to the skin depth, which is a measure of the high-frequency power supplied from the high-frequency power supply 42 entering the plasma P. The skin depth of the plasma can be calculated by the following equation (1). δ=(c / ω p ) …(1) Here, δ is the skin depth, c is the speed of light, ω p is the electron plasma frequency, and is expressed by the following equation (2). ω p =(n e e 2 / mε0) 1 / 2 …(2) However, n e is the electron density, e is the charge, m is the mass of the electron, and εo is the dielectric constant of vacuum. The electron density in the plasma can be measured by a Langmuir probe or the like.

[0030] <Film Quality Control Experiment 1: High-Frequency Power Supply or Non-Supply for Bias> First, we will explain the effects of (ii) supplying high-frequency power for bias and not supplying it, and in the former case, the effects of (iii) changing the high-frequency power for bias, with reference to Figures 3 to 5.

[0031] As previously described, DLC films are deposited using ions in the plasma of the deposition gas. Even with the conventional 13.56 MHz high-frequency power, in ion-based film deposition, it is common to supply high-frequency power for biasing to the mounting stage 21 and to pull the ions in the plasma toward the wafer W side.

[0032] Therefore, the high-frequency power for biasing (13.56 MHz within the range of 3 to 30 MHz) was varied (Experimental Example 1-1: 1000 W, Experimental Example 1-2: 400 W) and not supplied (Experimental Example 1-3: 0 W), and the ion energy density in the plasma, structural analysis of the obtained DLC film, film stress measurement, and dry etching rate were measured.

[0033] The parameters for the film deposition process were as follows: pressure inside the processing vessel 10 was 20 mTorr (2.67 Pa), C2H2 gas supply flow rate was 20 sccm, Ar gas supply flow rate was 180 sccm, wafer W heating temperature was 100°C, frequency of high-frequency power supplied from high-frequency power supply 42 was 180 MHz, supply power (hereinafter also referred to as "plasma supply power") was 1000 W, and electrode gap G = 30 mm (ratio G / δ = 4.5 to plasma skin depth δ = 7 mm).

[0034] Ion energy density was measured using a multi-grid analyzer, a multimeter (ADCMT, 7352A), and a source meter (KEITHREY, 2410). The structure of the obtained DLC film was analyzed using Raman light. Film stress was measured using an FLX-type stress meter (Toho Technology Co., Ltd.), and the dry etching rate was determined from the change in DLC film thickness before and after dry etching with CF-based gas.

[0035] Figure 3 shows the ion energy distribution in the plasma when the high-frequency power for biasing (hereinafter also referred to as "bias power") is varied. In Figure 3, the horizontal axis represents the relative magnitude of ion energy, and the vertical axis represents the relative magnitude of current density. In the figure, the thick solid line shows the ion energy distribution for Experimental Example 1-1, the dashed line shows the ion energy distribution for Experimental Example 1-2, and the thin solid line shows the ion energy distribution for Experimental Example 1-3. For each experimental example in Figure 3, the values ​​of plasma supply power and bias power are listed in that order.

[0036] As shown in Figure 3, in Experiment Example 1-1, where the high-frequency power for biasing was set to 1000W, the average ion energy contained in the plasma was higher compared to the other examples (Experiment Examples 1-2 and 3). Furthermore, the ion energy distribution was the broadest and contained two relatively small peaks.

[0037] On the other hand, in experimental examples 1-3, where high-frequency power for biasing is not supplied, the average ion energy contained in the plasma is relatively small. Furthermore, the distribution of ion energy is a sharp, unimodal distribution, with ions concentrated within a relatively narrow range of ion energies, centered around a single peak.

[0038] Furthermore, in Experimental Example 1-2, where the bias high-frequency power was 400W, both the average value of the ion energy and the width of the ion energy distribution were between the values ​​of the other examples (Experimental Examples 1-1 and 3). The ion energy distribution, in particular, contained two relatively small peaks, resulting in a shape similar to that of Experimental Example 1-1.

[0039] Next, Figure 4 shows the results (Raman spectra) of Raman light analysis performed on DLC films deposited under each of the conditions in Experimental Examples 1-1 to 1-3. In Figure 4, the horizontal axis represents the Raman shift, which indicates the difference in wavenumber between incident and scattered light, and the vertical axis represents the intensity of scattered light (in arbitrary units). Similar to Figure 3, the thick solid line shows the Raman spectrum of Experimental Example 1-1, the dashed line shows the spectrum of Experimental Example 1-2, and the thin solid line shows the spectrum of Experimental Example 1-3.

[0040] In the Raman spectrum, carbon atoms in a diamond structure have a Raman shift wavenumber of 1500 cm⁻¹. -1 Scattering increases in the region near this wavenumber. Therefore, the more concentrated the Raman spectrum is around this wavenumber, the closer it is to a diamond structure, and the higher the quality of the DLC film.

[0041] Looking at Figure 4 from this perspective, experimental example 1-3 (high frequency power for bias: 0W), shown by the thin solid line, has a Raman shift wavenumber of 1500 cm⁻¹. -1 High-intensity scattered light was detected in the high-wavenumber region (hereinafter also referred to as the "base region") outside the immediate vicinity of the base. This suggests that the film contains a relatively large amount of carbon atoms other than those in the diamond structure, as well as impurities, and that a polymeric carbon-containing film (PLC: Polymer Like Carbon) rather than a DLC film has been deposited.

[0042] On the other hand, the Raman spectra of experimental examples 1-1 and 1-2 show a Raman shift wavenumber of 1500 cm compared to experimental example 1-3. -1 The spectral shape is concentrated in the vicinity of the base region. From this perspective, it can be evaluated that a DLC film with good film quality has been obtained, with a relatively low impurity content and a large amount of carbon atoms in the diamond structure. In particular, the results of Experimental Example 1-1 show that the scattered light intensity in the base region is kept low.

[0043] Figure 5 shows the measurement results of film stress and dry etching rate for the DLC films obtained in experimental examples 1-1 to 1-3. The horizontal axis of Figure 5 represents the high-frequency power used for biasing. The left vertical axis represents the film stress value of the DLC film, and the right vertical axis represents the dry etching rate value. In the figure, the film stress measurement results are shown as square plots, and the dry etching rate measurement results are shown as diamond plots. The lower the film stress value (the larger the absolute value), the more likely it is that a well-tightened, high-density, and highly etching-resistant DLC film can be obtained.

[0044] As evaluated by the Raman spectrum measurement results in Figure 4, the DLC films obtained in Experimental Examples 1-1 and 1-2, which formed higher quality DLC films, had a higher film density. high Furthermore, the dry etching rate is low. In contrast, the DLC films obtained in Experimental Examples 1-3 have a small absolute value of film stress and a high dry etching rate.

[0045] Based on the results of Experimental Examples 1-1 to 1-3, as confirmed using Figures 3 to 5, it can be said that a higher quality DLC film is obtained when a sufficiently large bias high-frequency power is supplied (Experimental Examples 1-1 and 1-2) compared to when no bias high-frequency power is supplied (Experimental Example 1-3).

[0046] Therefore, it appears that by increasing the plasma power supplied from the high-frequency power supply 42 under conditions where high-frequency power is supplied for biasing, it may be possible to deposit a DLC film of good quality at a fast deposition rate. However, as shown by the circular plot in Figure 10 (described later), when the plasma supply power is increased under conditions where the bias high-frequency power is fixed at 1000W, the film density of the DLC film gradually decreases, reaching the target value of 2.0 g / cm³. 3 It was found that the rate fell below this level. Furthermore, as shown by the circular plots in Figure 12, which will be discussed later, the deposition rate of the DLC film gradually increases with increasing plasma power, and then tends to saturate.

[0047] As confirmed above, under conditions where high-frequency power is supplied for biasing, it was found that there is no simple correlation between increasing the plasma supply power in the VHF band and obtaining a high-density DLC film at a high deposition rate. Therefore, we will now examine in more detail the effects of changing the film deposition conditions under the condition that high-frequency power for bias is not supplied.

[0048] <Membrane Quality Control Experiment 2: Single-Frequency Supply> Figures 6A to 7C show the measurement results of the ion energy distribution in the plasma and the Raman spectra of the DLC film when (ii) high-frequency power for biasing is not supplied (hereinafter also referred to as "single-frequency supply" from the high-frequency power supply 42), (iv) the electrode gap is different, and (i) the power supplied from the high-frequency power supply 42 is changed.

[0049] Figures 6A to 6C show the measured ion energy distribution under electrode gap conditions G=30mm (G / δ=4.5), G=20mm (G / δ=2.9), and G=10mm (G / δ=1.4), when the plasma supply power from the high-frequency power supply 42 was varied to 1000W, 500W, and 200W. Other process conditions are the same as those described in Experimental Example 1-3. The horizontal and vertical axes in each figure are the same as in Figure 3, with the thick solid line showing the ion energy distribution for a plasma supply power of 1000W, the dashed line for 500W, and the thin solid line for 200W.

[0050] Figures 7A to 7C show the Raman spectra of DLC films deposited under electrode gap conditions G = 30 mm, 20 mm, and 10 mm, with the plasma supply power from the high-frequency power supply 42 varied to 500 W and 2500 W. Other process conditions are the same as those described in Experimental Examples 1-3. The horizontal and vertical axes in each figure are the same as in Figure 4, with the solid line showing the Raman spectrum for a plasma supply power of 500W and the dashed line showing the spectrum for 2500W.

[0051] The ion energy distribution shapes under each condition shown in Figures 6A to 6C all exhibit a sharp, unimodal distribution, with ions concentrated within a relatively narrow ion energy range. On the other hand, the change in the ion energy distribution when the plasma power supplied from the high-frequency power supply 42 is varied behaves differently depending on the size of the electrode gap.

[0052] In other words, in Figure 6A, where the electrode gap G = 30 mm, as the plasma supply power is increased from 200 W to 500 W to 1000 W, the position of the peak in the ion energy distribution gradually shifts to the lower energy side. At this time, the height of the peak in the ion energy distribution does not change very much depending on the magnitude of the plasma supply power.

[0053] On the other hand, in Figures 6B (electrode gap G=20mm) and 6C (G=10mm), the peak position of the ion energy distribution shifts to the higher energy side in response to the increase in plasma supply power. Furthermore, in Figure 6B, the peak height of the ion energy distribution is highest when the plasma supply power is 500W, followed by 1000W, and then lowest at 200W. In contrast, in Figure 6C, there is a tendency for the peak to gradually increase as the plasma supply power increases.

[0054] In the case of single-frequency supply without supplying high-frequency power for biasing, a single-peak ion energy distribution is obtained in all cases. On the other hand, the behavior of the change in the ion energy distribution in response to changes in plasma supply power differs from one another depending on the difference in electrode gap. Furthermore, the film quality of DLC films deposited under each condition also changes in response to these changes in ion energy distribution.

[0055] In other words, in Figure 7A (electrode gap G=30mm), the DLC film deposited under low plasma supply power conditions (500W) showed lower scattered light intensity in the base region of the Raman spectrum, indicating that a higher quality DLC film was obtained. on the other hand Figure 7B (electrode gap G = 20 mm) Furthermore, in DLC films deposited under high plasma power supply conditions (2500W), the scattered light intensity in the base region of the Raman spectrum is significantly reduced. In Figure 7C (electrode gap G=10mm), the DLC film deposited under high plasma supply power conditions (2500W) showed better performance. Compared to when the plasma supply power is low (500W), The scattered light intensity in the base region of the Raman spectrum is low.

[0056] <Overall Rating> The examples shown in Figures 7B and 7C confirm that there are conditions under which a DLC film with good film quality can be obtained by increasing the plasma supply power. This is achieved by supplying high-frequency power for biasing and increasing the plasma supply power. stomach This differs from the behavior of the circular plots in Figure 10, where the film density of the DLC film gradually decreases. In other words, the results in Figures 7B and 7C indicate that (iv) when the electrode gap is included as a control variable, there may be deposition conditions that allow for the deposition of a DLC film with good film quality while also achieving a high deposition rate.

[0057] The inventors believe that adjusting the ion energy distribution shown in Figures 3 and 6A to 6C is crucial for achieving these film deposition conditions. Specifically, by forming the plasma so that the peak of this ion energy distribution corresponds to an appropriate ion energy, it is possible to obtain a high-quality DLC film even when the plasma supply power changes.

[0058] Furthermore, the experimental results in Figures 6A to 6C indicate that (iv) adjusting the electrode gap is a key control variable for adjusting the position of the peak in the ion energy distribution.

[0059] In particular, in the VHF and UHF bands, which have higher frequencies than conventional devices (e.g., 13.56 MHz), the skin depth relative to the plasma becomes smaller. In this case, if the electrode gap is large relative to the skin depth, there is a risk that a plasma with an ion energy distribution sufficient to obtain a good film quality and of sufficient size may not be formed between the mounting stage 21 and the gas shower head 3.

[0060] Therefore, the inventors focused on the ratio of the gap distance (electrode gap) between the lower electrode, the mounting base 21, and the upper electrode, the gas shower head 3, to the surface depth of the plasma formed between these electrodes. By adjusting the value of this ratio within an appropriate range, a high film deposition rate can be obtained while obtaining a high-quality DLC film.

[0061] Figures 8 to 13 show various characteristics of DLC films deposited under conditions where the plasma supply power was varied with the electrode gap as a parameter, both when high-frequency power for biasing was supplied (Figures 8, 10, and 12) and when high-frequency power for biasing was not supplied (Figures 9, 11, and 13). Figures 8 and 9 show the change in film stress of the DLC film, and Figures 10 and 11 show the change in film density of the DLC film. In the following explanation, the target value for the film density of the DLC film described above is 2.0 g / cm³. 3 The following explains the case where the settings are as described above. The dashed lines in Figures 10 and 11 indicate the target values, and DLC films plotted above these dashed lines have a film density that satisfies the target values. Figures 12 and 13 show the change in the film deposition rate of the DLC film.

[0062] As shown by the circular plots in Figure 8, for example, when high-frequency power is supplied for biasing and the electrode gap is 30 mm (G / δ = 4.5), as the plasma supply power is increased, the absolute value of the film stress of the DLC film gradually decreases and eventually saturates. Also, as shown by the circular plots in Figure 10, the change in film density of the DLC film under similar conditions shows behavior corresponding to the change in film stress. That is, as the plasma supply power is increased, the film density of the DLC film gradually decreases and eventually saturates. Furthermore, when the plasma supply power is 1000 W or more, the film density of the DLC film reaches the target value (2.0 g / cm³). 3 This value is lower than ).

[0063] Next, in the single-frequency example, data on the film density of the DLC film was obtained only when the electrode gap was 10 mm (G / δ = 1.4) and the plasma supply power was 2500 W (Figure 11). As shown in Figure 11, the film density of the DLC film deposited under these conditions exceeds the target value. Looking at the changes in film stress in Figure 9, which allows for comparison of the three electrode gaps, we can see that, when the plasma supply power is 2500W, the absolute value of the film stress tends to increase as the electrode gap decreases. For the DLC film plotted in Figure 11, the fact that the film density exceeds the target value can be evaluated as a result that reflects this state of film stress.

[0064] Furthermore, as shown in Figures 12 and 13, it was confirmed that, in both the case of supplying high-frequency power for biasing and the case of single-frequency power, increasing the plasma supply power tends to increase the film deposition rate regardless of the electrode gap.

[0065] The above points are summarized. According to the experimental results shown in Figure 9, in the case of single frequency, in the region where the plasma supply power is between 1000W and 2500W, it is preferable to set the electrode gap to G=20mm and 10mm, and the ratio of the electrode gap G to the plasma skin depth δ, G / δ, to 2.9 and 1.4, within the range of 1 to 4. This increases the absolute value of the film stress compared to the case where the electrode gap G=30mm, and accordingly, a DLC film with a high film density can be obtained. In particular, when the value of G / δ is 1.4 (G=10mm), within the range of 1 to 2, the target value of 2.0 g / cm³ is obtained. 3 It can be confirmed that the film density can be achieved (Figure 11).

[0066] Furthermore, according to the experimental results shown in Figure 8, when supplying high-frequency power for biasing, in the region where the plasma supply power is 1000W or more and 2500W or less, it is preferable to set the electrode gap to G=20mm and the ratio of the electrode gap G to the plasma skin depth δ G / δ to a range of 1 or more and 4 or less, preferably 2.9 within the range of 2 or more and 3 or less. Based on the film stress measurement results shown in Figure 8, it is estimated that compared to the case where the electrode gap G=30mm, the absolute value of the film stress can be increased and a DLC film with relatively high film density can be obtained. Furthermore, based on the experimental results explained using Figures 3 and 4, it is preferable to set the bias high-frequency power to a value within the range of 400W or more and 1000W or less.

[0067] Furthermore, while the above explanation has described the case where the skin depth δ is 7 mm, the range of applicable skin depths δ is not limited to this. It can be appropriately selected within the range where the ratio G / δ of the electrode gap G to the plasma skin depth δ is between 1 and 4. For example, in the range where the electrode gap G is 6 to 32 mm and the skin depth δ is 5.3 to 7.8 mm, each condition can be selected so that the ratio G / δ of the electrode gap G to the plasma skin depth δ is between 1 and 4.

[0068] Here, let's explain the basis for setting the skin depth range (δ: 5.3~7.8 mm) mentioned above. It is known that in the pressure range of 2~200 mTorr (0.27~26.7 Pa) in which DLC films are deposited, the skin depth values ​​in the VHF and UHF bands converge to a nearly constant value. Therefore, by supplying high-frequency power included in the VHF band within this pressure range to form a plasma and determining the electron density, the range of the plasma skin depth can be determined based on equations (1) and (2) described above.

[0069] Therefore, under an Ar gas supply atmosphere (Ar gas supply flow rate 450 sccm), the pressure inside the processing container 10 was set to 100 mTorr (13.3 Pa), the electrode gap G = 30 mm, and the plasma supply power was varied between 200 and 900 W to measure the plasma density (Ar ion density). In a plasma in equilibrium state, the Ar ion density and electron density are approximately equal, so the skin depth δ can be calculated based on equations (1) and (2).

[0070] Figure 14 shows the measured plasma density in relation to the plasma supply power. Based on these measurement results, a regression equation was derived, and the relationship between plasma density Y and plasma supply power could be expressed by equation (3) below. Y = 6 × 10 8 X-9×10 9 (R2 =0.9931) …(3) Then, based on equation (3), calculating the plasma density at a plasma supply power of 2500W, we get approximately 1.491 × 10⁻⁶. 12 [1 / cm 3 ]

[0071] In the above measurements, it was observed that saturation occurred around 900W. This suggests that not all of the supplied power is absorbed by the plasma, but rather leaks out into the space below the mounting base 21, for example. A similar trend is observed even when the electrode gap G is 30 mm or less. Furthermore, mixing other gases (e.g., hydrocarbon gases such as CxHy) with Ar gas tends to decrease the plasma density. Therefore, from these factors and equation (3), the plasma density is approximately 1.0 × 10⁻⁶. 12 [1 / cm 3 This can be considered the upper limit.

[0072] Based on the plasma density (≈electron density) measured experimentally or calculated using regression equations and estimations, the skin depth δ [mm] was calculated using equations (1) and (2). The correspondence between plasma density and skin depth is shown in Figure 15. According to these results, using high-frequency power in the VHF or UHF band, the plasma power range is between 1000W and 2500W (plasma density: approximately 5.9 × 10⁻⁶). 11 ~1.0×10 12 When plasma is formed within the specified range, the skin depth δ is found to vary in the range of approximately 5.3 to 7.8 mm. Furthermore, as explained in the experimental results described above, it was found that by setting the electrode gap G to a value within 1 to 4 times the range of this skin depth δ, a high-quality DLC film can be obtained at a high deposition rate.

[0073] <Effects> The film deposition apparatus 1 described above has the following effects: By using high-frequency power in the VHF or UHF band and setting the gap distance (electrode gap) between the mounting stage 21 and the gas shower head 3 to a distance within the range of 1 to 4 times the plasma surface depth, a high-quality DLC film can be deposited at a high deposition rate.

[0074] In particular, it has become clear that, in DLC film deposition using ions, it is possible to set conditions that yield good film quality and a high deposition rate even when using a single frequency without supplying the high-frequency power for biasing that was conventionally considered necessary. When high-frequency power for biasing is not supplied, the installation of the high-frequency power supply 44 for biasing and the matching unit 43 attached to it can be omitted, as shown in the deposition apparatus 1 in Figure 1, thereby reducing the equipment cost.

[0075] <Other Embodiments> The composition of the deposition gas supplied to the processing container 10 for forming the DLC film is not limited to the examples described above. For example, in addition to C2H2 gas, CH4 gas, C2H4 gas, C3H6 gas, C6H6 gas, or mixtures thereof may be used as raw materials for the DLC film. Furthermore, the carbon-containing film formed on the wafer W is not limited to a DLC film containing many carbon atoms with a diamond structure. For example, a carbon-containing film may be formed with a predetermined amount of methyl groups (CH3-) or methylene groups (CH2=) at the ends of the carbon atoms with a diamond structure. Moreover, the carbon-containing film is not limited to hard mask applications, but can also be used as a protective film, barrier film, or coating material.

[0076] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of Symbols]

[0077] 1 Film deposition equipment 10 Processing containers 21 Mounting platform 3 Gas shower head 42 High frequency power supply

Claims

1. An apparatus for depositing a carbon-containing film on a substrate, A mounting platform is provided inside the processing container on which the substrate is placed and which constitutes the lower electrode, The upper electrode comprises a gas shower head positioned in the processing container opposite the aforementioned stand, provided for supplying the carbon-containing film-forming gas into the processing container, and connected to a high-frequency power supply that supplies high-frequency power in the VHF or UHF band, The apparatus is configured such that the gap distance between the mounting base and the gas shower head is set to a distance within the range of 1 to 4 times the surface depth of the plasma of the film-forming gas, which is formed by supplying the film-forming gas from the gas shower head into the processing container and supplying high-frequency power from the high-frequency power supply to the upper electrode.

2. The apparatus according to claim 1, wherein the epidermal depth is within the range of 5.3 to 7.8 mm, and the gap distance is within the range of 6 to 31.2 mm.

3. The apparatus according to claim 1 or 2, wherein the high-frequency power in the VHF band or UHF band is within the range of 30 MHz to 3 GHz.

4. The apparatus according to any one of claims 1 to 3, wherein high-frequency power in the range of 1,000 to 2,500 W is supplied from the high-frequency power supply.

5. The apparatus according to any one of claims 1 to 4, wherein a high-frequency power supply for biasing is not connected to the lower electrode, and the lower electrode is grounded.

6. A high-frequency bias power supply that provides bias high-frequency power in the range of 3 to 30 MHz is connected to the lower electrode. The apparatus according to any one of claims 1 to 4, wherein a bias high-frequency power supply in the range of 400 to 1000 W is supplied to the lower electrode from the bias high-frequency power supply.

7. The carbon-containing film has a film density of 1.8 g / cm³. ３ The apparatus according to any one of claims 1 to 6, wherein the DLC (Diamond Like Carbon) film is as described above.

8. A method for forming a carbon-containing film on a substrate, The process involves transporting the substrate into a processing container which is equipped with a mounting platform on which the substrate is placed and which constitutes the lower electrode, and a gas shower head positioned opposite the mounting platform, which is provided for supplying the film-forming gas for the carbon-containing film and is connected to a high-frequency power supply that supplies high-frequency power in the VHF or UHF band, and which constitutes the upper electrode, and then placing the substrate onto the mounting platform. Next, the process includes supplying the film-forming gas from the gas showerhead into the processing container and supplying high-frequency power from the high-frequency power supply to the upper electrode to plasmaize the film-forming gas, thereby forming the carbon-containing film on the substrate. A method wherein the gap distance between the mounting base and the gas shower head is set to a distance within the range of 1 to 4 times the surface depth of the plasma.

9. The method according to claim 8, wherein the epidermal depth is within the range of 5.3 to 7.8 mm, and the gap distance is within the range of 6 to 31.2 mm.

10. The method according to claim 8 or 9, wherein the high-frequency power in the VHF band or UHF band is a frequency in the range of 30 MHz to 3 GHz.

11. The method according to any one of claims 8 to 10, wherein high-frequency power in the range of 1,000 to 2,500 W is supplied from the high-frequency power supply.

12. The method according to any one of claims 8 to 11, wherein a high-frequency power supply for biasing is not connected to the lower electrode, and the lower electrode is grounded.

13. A high-frequency bias power supply that provides bias high-frequency power in the range of 3 to 30 MHz is connected to the lower electrode. The method according to any one of claims 8 to 11, wherein in the step of forming the carbon-containing film, bias high-frequency power in the range of 400 to 1000 W is supplied from the bias high-frequency power supply to the lower electrode.

14. The carbon-containing film has a film density of 1.8 g / cm³. ３ The method according to any one of claims 8 to 13, wherein the DLC (Diamond Like Carbon) film is as described above.

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