Plasma processing method

Abstract

In order to provide a wafer processing method by which metal contaminants attached to the rear surface of a wafer can be removed without a pattern on the front surface of the wafer being damaged by plasma, the following configuration is adopted.　This plasma processing method comprises: a first step for plasma-processing a sample placed on a sample holder; a second step for forming a deposited film on the surface of the sample after the first step; and a third step for removing metal contaminants of the sample disposed above the sample holder by using plasma generated by a halogen element-containing gas after the second step.

Description

Plasma treatment method

[0001] The present invention relates to a plasma processing method.

[0002] In semiconductor devices, miniaturization and three-dimensional device structures are progressing due to demands for lower power consumption and increased memory capacity. Furthermore, as cutting-edge devices become more sophisticated, standards for controlling metal contamination on wafers are becoming stricter, and these standards are expected to become even stricter in the future. Furthermore, these contamination standards require strict specifications not only for the front surface of the wafer where patterns are formed, but also for the back surface, necessitating technology to reduce back surface contamination.

[0003] In the manufacture of these semiconductor devices, semiconductor chips are fabricated by repeatedly performing processes using multiple semiconductor manufacturing equipment, such as exposure equipment, heat treatment equipment, dry etching equipment, wet cleaning equipment, film deposition equipment, and CMP (Chemical Mechanical Polishing) equipment, to form the desired patterns on the entire surface of the wafer. In particular, plasma-based processes are widely used in dry etching equipment, including anisotropic processing equipment that actively utilizes ions and radicals in plasma and isotropic processing equipment that actively utilizes radicals in plasma. Furthermore, in single-wafer processing equipment, in which the wafer to be processed is placed on a wafer stage and a specific process is performed on each wafer, precision processing of the patterns formed on the wafer surface is achieved by controlling the temperature of the wafer stage surface. However, controlling the wafer temperature requires contact between the backside of the wafer and the wafer stage, which can lead to metal contamination caused by metal from the wafer stage itself or the wafer stage surface adhering to the backside of the wafer during contact. Therefore, a processing method that reduces backside metal contamination is needed.

[0004] As a method for treating the back surface of a wafer, Patent Document 1 discloses a method in which a wafer coated with resist on its surface is raised by a pusher, charged particles in the plasma are removed with a mesh made of aluminum or the like, and then radicals in the plasma are actively irradiated to remove polysilicon formed on the back surface of the wafer.

[0005] Japanese Patent Application Publication No. 10-22276

[0006] In a method in which radicals in plasma are irradiated onto the backside of a wafer by lifting the wafer with a pusher, radicals or plasma are also irradiated onto the front side of the wafer on which a pattern is formed. Therefore, in the invention described in Patent Document 1, the front side of the wafer is separately coated with resist before being loaded into the equipment to protect the front side pattern. In other words, to remove metal contaminants from the backside of the wafer after dry etching, after performing the required processing on the pattern on the front side of the wafer by dry etching, the wafer must be removed once and coated with resist, and then loaded into a vacuum equipment to remove the film on the backside of the wafer. Therefore, the increased processing time per wafer due to the need to load and unload the wafer into the vacuum chamber was an issue.

[0007] An object of the present invention is to provide a plasma processing method that can remove metal contaminants adhering to the rear surface of a wafer by contacting the wafer with a wafer stage without damaging the pattern on the wafer surface with plasma.

[0008] The present invention provides a plasma processing method that solves the above-described problems, including: a semiconductor element forming step of performing a predetermined semiconductor element forming process on a target wafer while the target wafer is placed on a wafer stage in a vacuum chamber, a deposited film forming step of forming a deposited film on the target wafer while the target wafer is placed on the wafer stage after the semiconductor element forming step, and a halogen plasma processing step of separating the target wafer from the wafer stage after the deposited film forming step, and treating the target wafer with halogen plasma while the target wafer is separated from the wafer stage.

[0009] The plasma processing method also includes a semiconductor element forming process in which, in a vacuum chamber, a predetermined semiconductor element forming process is performed on the wafer to be processed while the wafer is placed on a wafer stage; a C deposited film forming process in which, after the semiconductor element forming process, a C deposited film is formed on the wafer to be processed using plasma containing a C-containing gas while the wafer is placed on the wafer stage; a halogen plasma processing process in which, after the deposited film forming process, the wafer to be processed is separated from the wafer stage and, while the wafer to be processed is separated from the wafer stage, the wafer to be processed is treated with halogen plasma; and a C deposited film removal process in which, after the halogen plasma processing process, a C deposited film formed on the wafer to be processed is removed using plasma containing an oxygen-containing gas.

[0010] The plasma processing method also includes a first deposition film formation step of forming a first deposition film on the wafer to be processed while the wafer is separated from the wafer stage in a vacuum chamber; a semiconductor element formation step of placing the wafer to be processed on the wafer stage after the first deposition film formation step, and performing a predetermined semiconductor element formation process on the wafer to be processed while the wafer is placed on the wafer stage; a second deposition film formation step of forming a second deposition film on the wafer to be processed while the wafer is placed on the wafer stage after the semiconductor element formation step; and a first deposition film removal step of separating the wafer to be processed from the wafer stage after the second deposition film formation step, and removing the first deposition film on the wafer to be processed while the wafer is separated from the wafer stage.

[0011] According to the present invention, it is possible to provide a plasma processing method that can remove metal contaminants adhering to the rear surface of a wafer by contacting the wafer with a wafer stage without damaging the pattern on the wafer surface with plasma.

[0012] Fig. 1 is a diagram showing an example of an apparatus configuration capable of implementing an embodiment of the present invention. Fig. 2 is a first typical time sequence diagram according to Example 1. Fig. 3 is a diagram showing a state in which a wafer to be etched is lifted by a pusher. Fig. 4 is a second typical time sequence diagram according to Example 1. Fig. 5 is a first typical time sequence diagram according to Example 2. Fig. 6 is a second typical time sequence diagram according to Example 2. Fig. 7 is a typical time sequence diagram according to Example 3.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] A first embodiment of the present invention will be described with reference to Figures 1 to 4. Figure 1 shows a typical apparatus structure for realizing this embodiment, which uses an electron cyclotron resonance plasma source. Figure 2 shows a first time sequence diagram using this embodiment. Figure 3 shows the apparatus state during the backside removal step of Figure 2. Figure 4 shows a second time sequence diagram using this embodiment. Note that this embodiment describes a plasma source using electron cyclotron resonance, but this method is not limited to plasma sources using electron cyclotron resonance. It can also be applied to plasma sources using inductive coupling or parallel plate systems, as long as the device can irradiate the wafer to be etched with plasma radicals preferentially over charged particles in the plasma by inserting an ion shield or the like.

[0015] 1, a separation plate 1002 is installed inside a vacuum vessel 1001, and the separation plate 1002 separates the interior of the vacuum vessel into an upper first space 1003 (as will be described later, this "first space" constitutes an "upper plasma generation chamber") and a lower second space 1004 (as will be described later, this "second space" constitutes a "lower plasma generation chamber"). The second space 1004 is equipped with a wafer stage 1006 for placing a wafer 1005 to be etched, and the wafer 1005 can be processed by irradiating it with plasma or radicals generated in the plasma.

[0016] High frequency power 1007 generated by a high frequency power supply to generate plasma is transmitted from above the device into vacuum chamber 1001 via waveguide 1008 and cavity resonator 1009. Here, high frequency power 1007 to generate plasma has a frequency of 300 MHz to 300 GHz.

[0017] A process gas 1010 is introduced into the vacuum chamber by a predetermined method and exhausted from 1011 at the bottom of the vacuum chamber. At this time, the flow rate and exhaust speed of the process gas 1010 are appropriately monitored, and by controlling the flow rate and exhaust speed of the process gas in accordance with the monitored values, it is possible to maintain the inside of the vacuum chamber at a desired pressure.

[0018] The process gas introduced into the vacuum chamber generates and maintains plasma at a position where the high-frequency power 1007 and the static magnetic field generated by the static magnetic field coil 1012 cause electron cyclotron resonance. In this device configuration, the plasma generation position causing electron cyclotron resonance can be changed by adjusting the coil current value of the static magnetic field coil 1012. When the generation position is set in the first space 1003, neutral radicals formed in the plasma are preferentially supplied to the wafer to be etched. On the other hand, when the generation position is set in the second space 1004, the plasma is directly irradiated onto the wafer to be etched, enabling processing using ions, which are charged particles in the plasma, and neutral radicals. In other words, the separation plate 1002 can separate the plasma generation chamber into an upper plasma generation chamber formed by the first space 1003 and a lower plasma generation chamber formed by the second space 1004.

[0019] The wafer stage 1006 has a temperature control function and can be controlled to any temperature. The wafer stage 1006 also has the function of fixing the wafer to be etched on the wafer stage, and the function of supplying a thermally conductive gas such as He between the wafer to be etched 1005 and the wafer stage 1006, maintaining a pressure between the two at, for example, 0.1 kPa to 10 kPa. This thermally conductive gas improves the thermal conductivity between the wafer stage and the wafer to be etched, allowing the temperature of the wafer to be etched to be efficiently controlled even inside a vacuum chamber.

[0020] The function of fixing the wafer to be etched to the wafer stage is preferably to generate Johnson-Rahbek force or Coulomb force to fix it electrically (a technique called "electrostatic chuck"). This fixing method may also be achieved by connecting only one DC power supply to the wafer stage and constructing an electrical path from the wafer stage to ground via plasma. However, in order to securely fix the wafer to be etched without generating plasma directly above the wafer, as shown in FIG. 1, a first electrode 1013 and a second electrode 1014 to which a DC voltage is applied are installed within the wafer stage 1006, and by applying opposite positive and negative voltages to each, Al is applied to the electrode surfaces at this time to adjust the dielectric constant and electrical resistance. ２ O ３ It is desirable that the surface is coated with a ceramic material such as Ti or a metallic material such as Ti.

[0021] 1, it is desirable to connect a high-frequency power supply with a frequency of, for example, 10 kHz to 100 MHz to the wafer stage in order to actively attract ions formed in the plasma to the wafer to be etched. In this way, when plasma is generated in the second space 1004, high-frequency power can be supplied from the high-frequency power supply to the wafer stage, thereby realizing reactive ion etching using the ions and radicals in the plasma.

[0022] 1, a separation plate 1002 is installed to supply only radicals to the wafer to be etched. The separation plate may be constructed using a metal material such as aluminum, titanium, or SUS, and electrically connected to a ground or a DC or AC power supply to electrically shield positively charged ions and negatively charged electrons generated in the plasma, thereby supplying only radicals generated in the plasma to the wafer. However, in this case, the surface of the metal material is exposed to the plasma, causing the metal material to scatter, and metal contamination can deteriorate the electrical characteristics of the processed wafer, posing a problem during mass production.

[0023] One possible method for suppressing metal contamination is to coat the conductive material with a Si-containing oxide film, a Y-containing oxide film, or an Al-containing oxide film, thereby preventing the metal from coming into direct contact with the plasma. However, coating increases production costs, and if part of the coating film is lost during long-term processing, metal contamination may occur. Therefore, it is desirable for the structure of the separation plate 1002 to be made solely of a dielectric material such as a Si-containing oxide film, a Y-containing oxide film, or an Al-containing oxide film. In particular, quartz, which is an Si-containing oxide film, does not contain metals such as Y or Al inside, making it a desirable dielectric material for suppressing metal contamination.

[0024] 1 shows the use of only one separator plate, but a structure combining multiple separator plates is also acceptable. However, it is desirable that one of the multiple separator plates has a hole on its outer periphery, i.e., outside half the radius of the separator plate. Furthermore, as long as there is a gap between the outside of the separator plate and the chamber wall, the structure and area of ​​the gap are not limited to a hole structure and are not particularly important.

[0025] Next, a method for suppressing metal contamination on the back surface of a wafer due to contact between the wafer to be etched and the wafer stage using the apparatus of FIG. 1 and the time sequence of FIG. 2 will be described.

[0026] First, as shown in (21) of Figure 2, the wafer to be etched 1005 is loaded onto the wafer stage 1006. When loading the wafer, the wafer to be etched 1005 is loaded onto a transfer arm from a transfer chamber held under vacuum onto the wafer stage 1006, and three or more pushers (not shown) provided in the wafer stage are raised to lift the wafer to be etched from the transfer arm. Thereafter, the transfer arm is retracted into the transfer chamber, and the pushers holding the wafer to be etched are lowered into the wafer stage, thereby placing the wafer to be etched on the wafer stage.

[0027] In this case, it is difficult to reduce the contact area between the backside of the wafer and the wafer stage to zero, and metal from the wafer stage itself or the surface of the wafer stage may adhere to the backside of the wafer during contact, which could result in metal contaminants adhering to the backside of the wafer.

[0028] Next, as shown in (22) of Figure 2, an etching process is performed under predetermined conditions, i.e., a process for forming semiconductor elements on the wafer to be etched by etching. During this process, the wafer to be etched 1005 is electrically fixed on the wafer stage 1006 by applying opposite positive and negative DC voltages to the first electrode 1013 and the second electrode 1014 installed in the wafer stage. It is desirable to apply the same positive and negative voltages, but it is also possible to apply either a positive or negative voltage to the first electrode 1013.

[0029] This keeps the wafer to be etched fixed on the wafer stage until the electrical fixation is released, thereby suppressing the generation of foreign matter caused by wear on the wafer to be etched and the wafer stage due to movement of the wafer to be etched caused by pressure fluctuations during the process, etc.

[0030] Furthermore, after the wafer to be etched is fixed on the wafer stage, it is desirable to introduce a thermally conductive gas such as He between the wafer to be etched and the wafer stage, and maintain a pressure of 0.1 kPa to 10 kPa between the wafer to be etched and the wafer stage. This thermally conductive gas improves the thermal conductivity between the wafer stage and the wafer to be etched, and even in a vacuum chamber, the temperature of the wafer to be etched can be efficiently controlled at a set temperature by using the temperature control function provided on the wafer stage. Note that, to prevent foreign matter from entering the hole through which the thermally conductive gas is introduced, the thermally conductive gas may be constantly flowing regardless of whether or not there is a wafer to be etched on the wafer stage. Furthermore, when no wafer to be etched is placed on the wafer stage, not only highly thermally conductive He gas but also N gas may be used. ２ It is also possible to prevent the inclusion of foreign matter by flowing a gas such as Ar.

[0031] During the etching process shown in Figure 2 (22), the plasma generation position in the vacuum chamber and the etching gas used are controlled to achieve the desired etching shape. However, as long as the desired shape can be achieved, the control method is not particularly important. In other words, the plasma generation position can be formed in either the upper plasma generation chamber or the lower plasma generation chamber, or it can be alternated between the two. It is also desirable to change the plasma generation position and the process gas used depending on the film to be etched. Note that during the etching process shown in Figure 2 (22), plasma is generated in the lower plasma generation chamber immediately after it is generated in the upper plasma generation chamber. However, it is also possible to interrupt plasma generation after plasma generation in the upper plasma generation chamber and then generate plasma in the lower plasma generation chamber.

[0032] Furthermore, in order to actively irradiate ions onto the wafer to be etched during the etching process (22), high-frequency power may be applied from a high-frequency power supply connected to the wafer stage. However, since there are almost no ions to be attracted to the wafer to be etched when plasma is generated in the upper plasma generation chamber, it is desirable to apply high-frequency power from a high-frequency power supply connected to the wafer stage only when plasma is generated in the lower plasma generation chamber.

[0033] Next, as shown in (23) of FIG. 2, a deposition film is formed on the wafer to be etched under predetermined conditions. In this process, SiCl ４ and SiH ４ and Si ２ H ６It is desirable to use a Si-containing gas containing, for example, SiO 2 . The location of the plasma generation is not particularly important in this case. However, if the plasma generation chamber is the lower plasma generation chamber, ions in the plasma may irradiate the wafer to be etched and cause damage if the deposited film is thin. Therefore, it is desirable to generate the plasma in the upper plasma generation chamber. Furthermore, if the deposited film is too thin, the pattern below the deposited film will be oxidized in the subsequent oxidation process, and if the deposited film is too thick, film peeling will occur due to film stress. Therefore, the thickness of the deposited film is desirably 5 nm to 100 nm. To form a hard deposited film, it is acceptable to use multiple steps: when the deposited film thickness is less than 5 nm, plasma is generated in the upper plasma generation chamber, and once the deposited film thickness reaches 5 nm or more, plasma is generated in the lower plasma generation chamber. However, to control the wafer temperature in this process, it is desirable to electrically secure the wafer to be etched to the wafer stage, and to introduce a thermally conductive gas such as He between the wafer to be etched and the wafer stage, maintaining a constant pressure.

[0034] Next, as shown in (24) of FIG. 2, the Si-based deposited film formed on the wafer to be etched is etched with a Si-containing gas. ２ YaCO ２The Si-based deposited film is oxidized by oxygen plasma generated by plasmatizing an oxygen-containing gas such as SiO . While oxygen plasma can be generated in the upper plasma generation chamber, it is preferable to oxidize the Si-based deposited film in the lower plasma generation chamber because oxygen ions generated in the oxygen plasma promote oxidation. Alternatively, high-frequency power can be applied from a high-frequency power source connected to the wafer stage to actively attract oxygen ions in the plasma and promote oxidation. However, to control the wafer temperature in this process, it is preferable to electrically secure the wafer to the wafer stage and introduce a thermally conductive gas such as He between the wafer and the wafer stage to maintain a constant pressure. In addition, in FIG. 2, after the Si deposited film is formed in (23), the Si deposited film is oxidized in (24). However, a Si-containing gas and an oxygen-containing gas can also be supplied simultaneously, and a plasma can be generated in the upper plasma generation chamber 1003 or the lower plasma generation chamber 1004 to deposit the Si oxide film. However, in this case, if a material such as carbon is exposed in the pattern created in the etching process (22), oxygen radicals may cause deformation of the processed shape. Therefore, depending on the pattern configuration, it is preferable to perform the formation of the Si deposited film (23) and the oxidation of the Si deposited film (24) as separate steps.

[0035] Next, in the metal film removal step shown in (25) of Figure 2, the metal film adhered to the wafer backside is removed by contacting the wafer stage with the wafer backside in step (21). At this time, after the thermal conduction gas introduced between the wafer to be etched and the wafer stage is stopped, the DC voltage applied to the first electrode 1013 and the second electrode 1014 is set to zero to release the electrical connection between the wafer to be etched and the wafer stage. The pusher is then raised while plasma is still being generated in the lower plasma generation chamber, leaving the wafer to be etched 1005 lifted by the pusher 3001, as shown in Figure 3. Even after the DC voltage applied to the electrodes is set to zero, residual charges accumulated in the electrodes and the wafer to be etched may not completely release the wafer from its fixed position, potentially resulting in wafer slippage or damage when the pusher is raised. However, by raising the pusher while generating plasma in the lower plasma generation chamber, the residual charges are removed by charged particles in the plasma, preventing the wafer from slipping or being damaged when the pusher is raised.

[0036] The plasma formed in the lower plasma formation chamber (25) in Figure 2 is preferably a halogen-based plasma containing F or Cl, which is known to remove metal films. The Si oxide film formed in (24) and (25) is known to be highly resistant to Cl plasma, and this prevents the pattern on the wafer surface from being directly exposed to the halogen-based plasma while the metal contaminants adhering to the backside are being removed.

[0037] However, in this structure, to prevent the pusher 3001 from being worn down by direct contact with charged particles in the halogen-based plasma, as in the backside metal removal step (41) in Figure 4, the pusher may be raised while plasma is generated using a rare gas such as Ar in the lower plasma generation chamber, and after the wafer to be etched is raised, a halogen-based plasma containing Cl elements may be generated in the upper plasma generation chamber to remove metal contaminants attached to the backside. Even in this case, the Si oxide film formed in (24) and (25) is known to be highly resistant to Cl radicals, and this prevents the pattern on the wafer surface from being directly exposed to the halogen-based plasma while the metal contaminants attached to the backside are being removed. Note that the steps in Figure 4 other than (41) are the same as those in Figure 2, and therefore detailed descriptions are omitted.

[0038] Next, in step (26) of Figure 2, the wafer to be etched is unloaded from the vacuum chamber. When unloading the wafer, for example, three or more pushers (not shown) provided in the wafer stage 1006 are raised, and the wafer to be etched 1005 is maintained in a lifted state while the transfer arm is loaded from the transfer chamber. At this time, to prevent contact between the wafer to be etched 1005 and the transfer arm, the wafer to be etched 1005 needs to be lifted to a position higher than the transferred transfer arm. Then, the pushers are lowered into the wafer stage, allowing the wafer to be held by the transfer arm. Then, the transfer arm is retracted into the transfer chamber, allowing the wafer to be unloaded from the vacuum chamber 1001.

[0039] In this method, the wafer to be etched is carried out from the vacuum chamber with a Si-based deposition film deposited on the pattern. However, this Si-based deposition film can be easily removed by wet etching such as SC1 cleaning using a mixed solution of ammonia water and hydrogen peroxide water, or HF cleaning, and it has been confirmed that this does not cause any problems in subsequent processes.

[0040] Also, SiCl ４It has been found that when etching is performed using a plasma containing a mixture of gases generated in the upper plasma generation chamber, a deposited film of 5 nm or more can be formed while processing the material to be etched, such as SiGe. ４ When etching the target film with a process gas containing a silicon dioxide gas, steps (22) and (23) do not necessarily have to be separated, and etching and forming a silicon deposited film may be performed in the same step.

[0041] 2, the etching rates of the Si deposited film formed on the wafer according to the steps of Examples (23) and (24) and TiN as a representative example of the backside metal were compared using the conditions in Table 1. The etching rate of the TiN was 83 nm / min, while the etching rate of the Si deposited film was less than 0.1 nm / min, which is the measurement limit, confirming that the formed Si deposited film can remove metal contaminants from the backside while still functioning as a protective film. It was also confirmed that this Si deposited film can be easily removed by wet etching using HF and does not affect subsequent processes.

[0042] As described above, when a wafer is placed on the wafer stage, metal from the wafer stage itself or the surface of the wafer stage adheres to the back surface of the wafer upon contact, resulting in metal contaminants adhering to the back surface of the wafer. However, to protect the etched pattern, the wafer surface is coated with a Si deposition film, and then the wafer is lifted up with a pusher to create a gap between the wafer to be etched and the wafer stage, and a step of removing the back surface metal is performed, thereby achieving a process that reduces the amount of metal contamination on the back surface of the wafer.

[0043] As a second embodiment of the present invention, an example in which a C deposition film is used as the deposition film formed on the wafer surface after the etching process will be described with reference to Figure 5. As with the first embodiment, this embodiment uses the electron cyclotron resonance method shown in Figure 1 as the plasma source. However, similar embodiments can be realized when other plasma sources, such as an inductively coupled method or a parallel plate method, are used. Furthermore, similar processes to those in the first embodiment are denoted by the same symbols.

[0044] First, as shown in (21) of Figure 5, the wafer to be etched 1005 is loaded onto the wafer stage 1006. When loading the wafer, the wafer to be etched 1005 is loaded onto a transfer arm from a transfer chamber held under vacuum onto the wafer stage 1006, and three or more pushers (10 not shown) provided in the wafer stage are raised to lift the wafer to be etched 1005 from the transfer arm. Thereafter, the transfer arm is retracted into the transfer chamber, and the pushers holding the wafer to be etched 1005 are lowered onto the wafer stage 1006, thereby placing the wafer to be etched 1005 on the wafer stage 1006.

[0045] In this case, it is difficult to reduce the contact area between the back surface of the etched wafer 1005 and the wafer stage 1006 to zero, and metal from the wafer stage itself or the surface of the wafer stage may adhere to the back surface of the wafer during contact, which may result in metal contaminants adhering to the back surface of the wafer.

[0046] Next, as shown in (22) of Figure 5, an etching process is performed under predetermined conditions. At this time, opposite positive and negative DC voltages are applied to a first electrode 1013 and a second electrode 1014 installed in a wafer stage 1006, respectively, to electrically fix the wafer 1005 to be etched on the wafer stage 1006. It is desirable to apply the same positive and negative voltages, but it is also possible to apply either a positive or negative voltage to the first electrode 1013.

[0047] This keeps the wafer 1005 to be etched fixed on the wafer stage 1006 until the electrical fixation is released, thereby suppressing the generation of foreign matter due to wear between the wafer to be etched and the wafer stage caused by the movement of the wafer to be etched due to pressure fluctuations during the process, etc.

[0048] Furthermore, after the wafer 1005 to be etched is fixed on the wafer stage 1006, it is desirable to introduce a thermally conductive gas such as He between the wafer to be etched and the wafer stage, and maintain a pressure of 0.1 kPa to 10 kPa between the wafer to be etched and the wafer stage. This thermally conductive gas improves the thermal conductivity between the wafer stage and the wafer to be etched, and even in a vacuum chamber, the temperature of the wafer to be etched can be efficiently controlled at a set temperature by using the temperature control function provided on the wafer stage. Note that to prevent foreign matter from entering the hole through which the thermally conductive gas is introduced, the thermally conductive gas may be constantly flowing regardless of whether or not there is a wafer to be etched on the wafer stage. When no wafer to be etched is placed on the wafer stage, not only He gas with high thermal conductivity but also N gas may be used. ２ It is also possible to prevent the inclusion of foreign matter by flowing a gas such as Ar.

[0049] Furthermore, during the etching process (22), the plasma generation position in the vacuum chamber and the etching gas used are controlled to achieve the desired etching shape. However, as long as the desired shape can be achieved, the control method is not particularly important. In other words, the plasma generation position may be formed in either the upper plasma generation chamber or the lower plasma generation chamber, or may alternate between the two. Furthermore, it is desirable to change the plasma generation position and the process gas used depending on the film to be etched. Note that during the etching process of Figure 5 (22), plasma is always generated in either the upper or lower plasma generation chamber, but plasma generation or the supply of process gas may be interrupted between steps.

[0050] Furthermore, in order to actively irradiate ions onto the wafer to be etched during the etching process (22), high-frequency power may be applied from a high-frequency power supply connected to the wafer stage. However, since there are almost no ions to be attracted to the wafer to be etched when plasma is generated in the upper plasma generation chamber, it is desirable to apply high-frequency power from a high-frequency power supply connected to the wafer stage only when plasma is generated in the lower plasma generation chamber.

[0051] Next, as shown in (51) of FIG. 5, a deposition film is formed on the wafer to be etched under predetermined conditions. In this process, ４ , C.H. ３ F, CHF ３ , C.F. ４ , C ４ F ６ , C ４ F ８ It is desirable to use a C-containing gas containing, for example, fluorine, arsenic, and nitric acid. In this case, the location where the plasma is generated is not particularly important, but if the plasma is generated in the lower plasma generation chamber, ions in the plasma may irradiate the wafer to be etched and cause damage if the deposited film is thin. Therefore, it is desirable to generate the plasma in the upper plasma generation chamber.

[0052] Furthermore, if the deposited film is too thin, etching damage may occur to the pattern below the deposited film during the subsequent backside metal removal process, and if the deposited film is too thick, film peeling may occur due to film stress. Therefore, a deposited film thickness of 5 nm to 100 nm is desirable. Furthermore, to form a hard deposited film, multiple steps may be used: when the deposited film thickness is less than 5 nm, plasma is generated in the upper plasma generation chamber, and once the deposited film thickness reaches 5 nm or more, plasma is generated in the lower plasma generation chamber. However, to control the wafer temperature in this process, it is desirable to electrically fix the etched wafer to the wafer stage and introduce a thermally conductive gas such as He between the etched wafer and the wafer stage, maintaining a constant pressure.

[0053] Next, in the metal film removal step shown in (25) of Figure 5, the metal film adhered to the wafer backside is removed by contacting the wafer stage with the wafer backside in step (21). At this time, after the thermal conduction gas introduced between the wafer to be etched and the wafer stage is stopped, the DC voltage applied to the first electrode 1013 and the second electrode 1014 is set to zero to release the electrical connection between the wafer to be etched and the wafer stage. The pusher is then raised while plasma is still being generated in the lower plasma generation chamber, leaving the wafer to be etched 1005 lifted by the pusher 3001, as shown in Figure 3. Even after the DC voltage applied to the electrodes is set to zero, residual charges accumulated in the electrodes and the wafer to be etched may not completely release the wafer from its fixed position, potentially resulting in wafer slippage or damage when the pusher is raised. However, by raising the pusher while generating plasma in the lower plasma generation chamber, the residual charges are removed by charged particles in the plasma, preventing the wafer from slipping or being damaged when the pusher is raised.

[0054] The plasma formed in the lower plasma formation chamber of Fig. 5 (25) is preferably a halogen-based plasma containing F or Cl, which is known to remove metal films. In this case, the C deposition film formed in Fig. 5 (51) is known to be highly resistant to Cl plasma, and this prevents the pattern on the wafer surface from being directly exposed to the halogen-based plasma while the metal contaminants adhering to the backside are being removed.

[0055] However, in this structure, to prevent the pusher 3001 from being worn down by direct contact with charged particles in the halogen-based plasma, instead of Figure 5 (25), as shown in Figure 6 (61), the pusher may be raised while plasma is generated using a rare gas such as Ar in the lower plasma generation chamber, and after the wafer to be etched is raised, a halogen-based plasma containing Cl element may be generated in the upper plasma generation chamber to remove metal contaminants attached to the backside. Even in this case, the C deposition film formed in Figure 5 (51) is known to be highly resistant to Cl radicals, so that the pattern on the wafer surface can be prevented from being directly exposed to the halogen-based plasma while the metal contaminants attached to the backside are being removed. Note that the steps in Figure 6 other than (61) are the same as those in Figure 2, and therefore detailed descriptions are omitted.

[0056] Next, in step (52) of FIG. ２ YaCO ２ Ya O ３ The C deposition film is removed using an oxygen-containing gas such as HCl. The pusher position in this process can be high or low, but it is desirable to remove the C deposition film while the pusher is elevated in order to reduce the increase in process time due to the up-and-down movement of the pusher. The plasma can be formed in either the upper or lower plasma generation chamber, but it is desirable to form the plasma in the upper plasma generation chamber in order to prevent damage to the formed pattern caused by irradiation with ions in the plasma after the C deposition film is removed.

[0057] Next, in step (26) of Figure 5, the wafer to be etched is unloaded from the vacuum chamber. When unloading the wafer, for example, three or more pushers (not shown) provided in the wafer stage 1006 are raised to lift the wafer to be etched 1005, and the wafer is then loaded from the transfer chamber by a transfer arm. At this time, to prevent contact between the wafer to be etched 1005 and the transfer arm, the wafer to be etched 1005 needs to be lifted to a higher position than the transferred transfer arm. Then, the pushers are lowered into the wafer stage, allowing the wafer to be held by the transfer arm. Then, the transfer arm is retracted into the transfer chamber, allowing the wafer to be unloaded from the vacuum chamber 1001.

[0058] In this method, the C deposition film is removed in the vacuum chamber and then the wafer is removed. However, the C deposition film removal step may be performed in a separate dry etching apparatus or wet etching apparatus after the wafer is removed.

[0059] As described above, when a wafer is placed on the wafer stage, metal from the wafer stage itself or the surface of the wafer stage may adhere to the back surface of the wafer upon contact, which can result in metal contaminants adhering to the back surface of the wafer. However, to protect the etched pattern, the wafer surface is coated with a carbon deposition film, and then the wafer is lifted up with a pusher to create a gap between the wafer to be etched and the wafer stage, and a step of removing the back surface metal is performed, thereby achieving a process that reduces the amount of metal contamination on the back surface of the wafer.

[0060] As a third embodiment of the present invention, an example in which a deposition film is formed on the backside of a wafer before an etching process will be described with reference to Figure 7. As with the first and second embodiments, this embodiment uses the electron cyclotron resonance method shown in Figure 1 as the plasma source. However, similar embodiments can be realized using other plasma sources, such as an inductively coupled method or a parallel plate method. Furthermore, processes similar to those in the first embodiment are denoted by the same symbols.

[0061] First, as shown in (71) of Figure 7, the wafer 1005 to be etched is loaded onto the wafer stage 1006. When loading the wafer, the wafer 1005 to be etched is loaded onto a transfer arm from a transfer chamber held under vacuum onto the wafer stage 1006, and three or more pushers (not shown) provided in the wafer stage are raised to lift the wafer to be etched from the transfer arm. The transfer arm is then retracted into the transfer chamber. At this time, the pushers holding the wafer to be etched are kept elevated, maintaining a state in which the backside of the wafer and the wafer stage are not in contact with each other.

[0062] Next, as shown in (72) of FIG. 7, a first deposition film is formed on the front and back surfaces of the wafer to be etched under predetermined conditions. In this process, the deposition film is CH ４ , C.H. ３ F, CHF ３ , C.F. ４ , C ４ F ６ , C ４ F ８ C-containing gas or SiCl ４ , SiH ４ , Si ２ H ６ It is desirable to use a Si-containing gas containing, for example, silicon dioxide. The location of the plasma generation is not particularly important. However, if the plasma generation chamber is the lower plasma generation chamber, ions in the plasma may irradiate the wafer to be etched and cause damage if the deposited film is thin. Therefore, it is desirable to generate the plasma in the upper plasma generation chamber. Furthermore, if the deposited film is too thin, etching damage will occur to the pattern below the deposited film during the subsequent backside metal removal process. If the deposited film is too thick, film peeling will occur due to film stress. Therefore, it is desirable for the thickness of the deposited film to be 5 nm or more and 100 nm or less. Furthermore, to form a hard deposited film, it is acceptable to use multiple steps: when the deposited film thickness is less than 5 nm, plasma is generated in the upper plasma generation chamber, and then plasma is generated in the lower plasma generation chamber after the deposited film thickness reaches 5 nm or more.

[0063] 7, the pusher holding the wafer to be etched is lowered into the wafer stage, whereby the wafer to be etched is placed on the wafer stage, and the first surface deposition film formed on the wafer surface is then removed. When placing the wafer to be etched on the wafer stage, it is difficult to eliminate the contact area between the back surface of the wafer and the wafer stage, and metal from the wafer stage itself or the surface of the wafer stage may adhere to the back surface of the wafer during contact, which can result in metal contaminants adhering to the back surface of the wafer. However, by performing the deposition film formation step of (72), the deposition of metal contaminants is limited to the back surface deposition film deposited on the back surface of the wafer, and the underlying wafer to be etched does not come into direct contact with the metal contaminants.

[0064] In this embodiment, the rare gas is kept flowing when the pusher is lowered, but this is to prevent foreign matter from adhering to the stage by creating a gas flow inside the chamber. Therefore, if there is no particular need, it is not necessary to keep the gas flowing when the pusher is lowered.

[0065] In the first surface deposition film removal step (73), the wafer to be etched is placed on a wafer stage, and then opposite positive and negative DC voltages are applied to a first electrode 1013 and a second electrode 1014 installed in the wafer stage, respectively, to electrically fix the wafer to be etched 1005 on the wafer stage 1006. While it is preferable to apply the same positive and negative voltages, it is also acceptable to apply either a positive or negative voltage to the first electrode 1013. This fixes the wafer to be etched on the wafer stage until the electrical fixation is released, and this makes it possible to suppress the generation of foreign matter due to wear of the wafer to be etched and the wafer stage caused by movement of the wafer to be etched due to pressure fluctuations during the process, etc.

[0066] Furthermore, after the wafer to be etched is fixed on the wafer stage, it is desirable to introduce a thermally conductive gas such as He between the wafer to be etched and the wafer stage, and maintain a pressure of 0.1 kPa to 10 kPa between the wafer to be etched and the wafer stage. This thermally conductive gas improves the thermal conductivity between the wafer stage and the wafer to be etched, and even in a vacuum chamber, the temperature of the wafer to be etched can be efficiently controlled at a set temperature by using the temperature control function provided on the wafer stage. Note that to prevent foreign matter from entering the hole through which the thermally conductive gas is introduced, the thermally conductive gas may be constantly flowing regardless of whether or not there is a wafer to be etched on the wafer stage. When no wafer to be etched is placed on the wafer stage, not only highly thermally conductive He gas but also N gas may be used. ２ It is also possible to prevent the inclusion of foreign matter by flowing a gas such as Ar.

[0067] In the first surface deposited film removal step (73), if a C-containing gas was used to form the deposited film in the first deposited film formation step (72), it is desirable to use a gas containing O, N, or H as the deposited film removal gas. Also, if a Si-containing gas was used to form the deposited film in the first deposited film formation step (72), it is desirable to use a gas containing H, F, Br, or Cl as the deposited film removal gas. However, the combination of gases selected is not particularly limited depending on the type of film to be etched.

[0068] Furthermore, in order to improve the efficiency of removing the deposited film, it is preferable to generate the plasma in the lower plasma generation chamber in the vicinity of the wafer to be etched, but it is also acceptable to generate the plasma in the upper plasma generation chamber as long as the deposited film can be removed at an acceptable rate.

[0069] Next, as shown in (74) of Figure 7, an etching process is performed under specified conditions. During this process, the wafer is fixed on the wafer stage and the heat transfer gas between the wafer to be etched and the wafer stage is maintained in the state shown in (73), and it is desirable to maintain a pressure of 0.1 kPa to 10 kPa between the wafer to be etched and the wafer stage. Furthermore, during the etching process (74), the plasma generation position within the vacuum chamber and the etching gas used are controlled to achieve the desired etching shape. However, as long as the desired shape can be achieved, the control method is not particularly important. In other words, the plasma generation position may be formed in either the upper plasma generation chamber or the lower plasma generation chamber, and may alternate between the two generation positions. Furthermore, the plasma generation position and the process gas used may be changed as many times as necessary depending on the film to be etched.

[0070] In the etching process shown in Figure 7 (74), plasma is generated in the lower plasma generation chamber, followed by plasma generation in the upper plasma generation chamber. However, plasma generation or supply of process gas may be interrupted between steps. If necessary, plasma may be generated only in either the upper or lower chambers for etching.

[0071] Furthermore, in order to actively irradiate the wafer to be etched with ions during the etching process (74), high-frequency power may be applied from a high-frequency power supply connected to the wafer stage. However, since there are almost no ions to be attracted to the wafer to be etched when plasma is generated in the upper plasma generation chamber, it is desirable to apply high-frequency power from a high-frequency power supply connected to the wafer stage only when plasma is generated in the lower plasma generation chamber.

[0072] Next, as shown in (23) of Fig. 7, a Si deposited film is formed on the wafer to be etched under predetermined conditions. ４ , SiH ４ , Si ２ H ６It is desirable to use a Si-containing gas containing, for example, SiO 2 . The location of the plasma generation is not particularly important in this case. However, if the plasma generation chamber is the lower plasma generation chamber, ions in the plasma may irradiate the wafer to be etched and cause damage if the deposited film is thin. Therefore, it is desirable to generate the plasma in the upper plasma generation chamber. Furthermore, if the deposited film is too thin, the pattern below the deposited film will be oxidized in the subsequent oxidation process, and if the deposited film is too thick, film peeling will occur due to film stress. Therefore, the thickness of the deposited film is desirably 5 nm to 100 nm. To form a hard deposited film, it is acceptable to use multiple steps: when the deposited film thickness is less than 5 nm, plasma is generated in the upper plasma generation chamber, and once the deposited film thickness reaches 5 nm or more, plasma is generated in the lower plasma generation chamber. However, to control the wafer temperature in this process, it is desirable to electrically secure the wafer to be etched to the wafer stage, and to introduce a thermally conductive gas such as He between the wafer to be etched and the wafer stage, maintaining a constant pressure.

[0073] Next, as shown in (24) of FIG. 7, the Si-based deposited film formed on the wafer to be etched is etched with a Si-containing gas. ２ YaCO ２The Si-based deposited film is oxidized by oxygen plasma generated by plasmatizing an oxygen-containing gas such as SiO . While oxygen plasma may be generated in the upper plasma generation chamber, it is preferable to oxidize the Si-based deposited film in the lower plasma generation chamber because oxygen ions generated in the oxygen plasma promote oxidation. Alternatively, oxidation may be promoted by actively attracting oxygen ions in the plasma through application of high-frequency power from a high-frequency power supply connected to the wafer stage. However, in this process, to control the wafer temperature, it is preferable to electrically secure the wafer to the wafer stage and introduce a thermally conductive gas such as He between the wafer and the wafer stage to maintain a constant pressure. In addition, in FIG. 7, after a Si deposited film is formed in (23), the Si deposited film is oxidized in (24). However, a Si-containing gas and an oxygen-containing gas may be simultaneously supplied, and a plasma may be generated in the upper plasma generation chamber 1003 or the lower plasma generation chamber 1004 to deposit a Si oxide film. However, in this case, if the pattern created in the etching process (74) contains materials such as carbon, there is a possibility that the processed shape may be changed by oxygen radicals. Therefore, it is preferable to perform the formation of the Si deposited film (23) and the oxidation of the Si deposited film (24) as separate processes.

[0074] Next, in step (75) of Figure 7, the first backside deposition film formed on the backside of the wafer to be etched is removed. After stopping the thermal conduction gas introduced between the wafer to be etched and the wafer stage, the DC voltage applied to the first electrode 1013 and the second electrode 1014 is reduced to zero, releasing the electrical connection between the wafer to be etched and the wafer stage. The pusher is then raised while plasma is generated using a rare gas in the lower plasma generation chamber, leaving the wafer to be etched 1005 lifted by the pusher 3001, as shown in Figure 3. Even after the DC voltage applied to the electrodes is reduced to zero, residual charges accumulated on the electrodes and the wafer to be etched may not completely release the wafer from its fixed position, potentially resulting in wafer slippage or damage when the pusher is raised. However, by raising the pusher while generating plasma in the lower plasma generation chamber, the residual charges are removed by charged particles in the plasma, preventing wafer slippage or damage when the pusher is raised.

[0075] 7 (75), if a C-containing gas is used to form a deposited film in the first deposited film formation step (72), it is desirable to use a gas containing O, N, or H as the deposited film removal gas. If a Si-containing gas is used to form a deposited film in the first deposited film formation step (72), it is desirable to use a gas containing H, F, Br, or Cl as the deposited film removal gas. However, the combination of gases selected is not particularly limited depending on the type of film to be etched.

[0076] Furthermore, in order to reduce processing damage to the wafer to be etched, it is preferable to generate plasma in the upper plasma generation chamber, but plasma may be generated in the lower plasma generation chamber as long as processing damage is within an allowable value.

[0077] Next, in step (26) of Figure 7, the wafer to be etched is unloaded from the vacuum chamber. When unloading the wafer, for example, three or more pushers (not shown) provided in the wafer stage 1006 are raised, and a transfer arm is loaded from the transfer chamber while the wafer to be etched 1005 is lifted. At this time, to prevent contact between the wafer to be etched 1005 and the transfer arm, the wafer to be etched 1005 needs to be lifted to a position higher than the transferred transfer arm. Then, by lowering the pushers into the wafer stage, the wafer to be etched can be held by the transfer arm. Then, by retracting the transfer arm into the transfer chamber, the wafer to be etched can be unloaded from the vacuum chamber 1001.

[0078] As described above, by using this embodiment, the deposition film formation process (72) is performed before the wafer to be etched is placed on the wafer stage, thereby limiting the deposition of metal contaminants to the back surface deposition film deposited on the back surface of the wafer, and realizing that the back surface of the wafer to be etched below that does not come into direct contact with the metal contaminants.Furthermore, by removing the metal contaminants together with the back surface deposition film deposited on the back surface of the wafer and then transporting the wafer to be etched, it is possible to reduce metal contamination on the back surface.

[0079] In this example, the method of removing the first backside deposition film in step (75) was described. However, before removing the first backside deposition film, a halogen-based plasma containing F or Cl, which is known to remove metal films, may be used to remove the metal film, and then the first backside metal film may be removed. This configuration allows for more reliable removal of the metal film on the backside of the wafer. Furthermore, in this example, the Si deposition film was formed after the etching process in step (74) in the same manner as the method of forming the Si deposition film described in Example 1. However, the method of forming the C deposition film after etching in Example 2 may also be used.

[0080] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0081] 1001: Vacuum vessel, 1002: Separation plate, 1003: First space, 1004: Second space, 1005: Wafer to be etched, 1006: Wafer stage, 1007: High frequency power, 1008: Waveguide, 1009: Cavity resonator, 1010: Process gas, 1011: Exhaust direction, 1012: Static magnetic field coil, 1013: First electrode, 1014: Second electrode.

Claims

1. A plasma processing method comprising: a first step of plasma processing a sample placed on a sample stage; a second step of forming a deposition film on the surface of the sample after the first step; and a third step of removing metal contaminants from the sample placed above the sample stage using plasma generated by a halogen-containing gas after the second step.

2. The plasma processing method according to claim 1, wherein the halogen-containing gas is a gas containing chlorine.

3. The plasma processing method according to claim 1, wherein the second step is carried out using plasma generated from a silicon-containing gas.

4. A plasma processing method according to claim 1, wherein the second step comprises a deposited film forming step of forming the deposited film with active neutral particles generated by using plasma, and a hardening step of hardening the deposited film with active neutral particles and ions generated by using plasma.

5. A plasma processing method according to claim 4, wherein the deposition film forming step is carried out using plasma generated from a silicon element-containing gas, and the hardening step is carried out using plasma generated from an oxygen element-containing gas.

6. The plasma processing method according to claim 3 or 5, wherein the silicon-containing gas is SiCl ４ Gas, SiH ４ Gas or Si ２ H ６ A plasma processing method characterized in that the gas is a plasma.

7. The plasma processing method according to claim 5, wherein the oxygen-containing gas is O ２ gas or CO ２ A plasma processing method characterized in that the gas is a plasma.

8. A plasma processing method according to claim 1, wherein the third step removes contaminants from the sample by using active neutral particles generated by using plasma.

9. A plasma processing method according to claim 1, characterized in that the third step is a step of generating plasma using a rare gas in the space below a shielding plate that blocks ions from entering the sample stage when the sample is raised from the sample stage, and generating plasma using the halogen-containing gas in the space above the shielding plate after the sample has been raised from the sample stage.

10. The plasma processing method according to claim 1, wherein the second step is carried out using plasma generated from a carbon-containing gas.

11. A plasma processing method according to claim 1, further comprising a fourth step of exposing the sample placed above the sample stage to plasma generated by an oxygen-containing gas, wherein the second step is carried out using plasma generated by a carbon-element-containing gas, and the plasma in the second step is generated in the space above a shielding plate that blocks ions from entering the sample stage.

12. A plasma processing method according to claim 11, characterized in that the third step is a step of generating plasma using a rare gas in the space below a shielding plate that blocks ions from entering the sample stage when the sample is raised from the sample stage, and generating plasma using the halogen-element-containing gas in the space above the shielding plate after the sample has been raised from the sample stage.

13. A plasma processing method comprising: a first step of forming a deposited film on the front and back surfaces of a sample; a second step of plasma processing the sample placed on a sample stage after the first step; a third step of forming a deposited film on the sample placed on the sample stage after the second step; and a fourth step of using plasma to remove the deposited film on the back surface of the sample placed above the sample stage after the third step.

14. The plasma processing method according to claim 13, wherein the plasma in the fourth step is generated using a gas containing a halogen element.

15. A plasma processing method according to any one of claims 1, 11 and 13, further comprising a step of wet etching the sample after the sample is removed from the processing chamber in which the sample is subjected to the plasma processing.

16. The plasma processing method according to claim 15, wherein the wet etching uses a mixed solution of ammonia water and hydrogen peroxide solution or hydrofluoric acid (HF).