JP6169666B2 - Plasma processing method - Google Patents

Description

  The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing method suitable for performing surface processing of a semiconductor substrate or the like using plasma.

  Due to miniaturization of recent semiconductor elements, higher accuracy in dimensional accuracy, that is, CD (Critical Dimension) accuracy is required for an etching process for transferring a mask formed by lithography onto a lower layer film. In addition to high CD controllability in mass production sites, ensuring CD reproducibility is an important issue. In general, the factors that cause the CD to fluctuate in the etching process are that reaction products generated from the material to be processed adhere to the inner wall of the etching chamber, the chamber member is consumed due to long-term use, and the temperature of the chamber member varies. For example, the probability of radicals adhering to the inner wall of the chamber changes, and the plasma state that affects the etching performance fluctuates.

Next, in the fine transistor, it is necessary to increase the capacity of the gate insulating film in order to control the short channel effect, and this problem has been achieved by reducing the thickness of the conventional gate oxide film. However, since the leakage current increases as the gate oxide film becomes thinner, a material having a higher dielectric constant (High-k) has been introduced as the gate insulating film. As a high-k material that replaces the oxide film, a hafnium oxide film (HfO ₂ ) can be given. However, since there is a material mismatch between the conventional polysilicon (Poly-Si) electrode and HfO ₂ , a structure having a metal film having an appropriate work function is required. There are various metal materials, but TiN, La, etc. are used as described in Semiconductor International 2008/1 (Non-Patent Document 1).

  Conventionally, plasma processing apparatuses have been cleaned using plasma for each wafer or lot, and for processes targeting carbon (C), oxide film, poly-Si, nitride film, etc., mainly fluorine ( F), chlorine (Cl), oxygen (O) containing or mixed plasma cleaning has been used. In addition, when metal or the like (for example, Al) generated by the consumption of the inner wall member of the etching chamber adheres to the chamber, it is difficult to remove it only by cleaning with plasma. Techniques such as keeping the chamber atmosphere constant have been studied. As an example of such a technique, one described in Japanese Patent Application Laid-Open No. 2004-031380 (Patent Document 1) is known.

  In addition, as in the technique described in US Pat. No. 7,204,913 (Patent Document 2), there is a technique in which a coating is applied to the reactor inner wall for each wafer processing to reduce the influence on the process performance due to the reactor inner wall state change. Are known.

  On the other hand, when a metal material (for example, TiN) is etched, as described in Journal of Vacuum Science and Technoloby B24, 2191 (2006) (Non-Patent Document 2), the metal material adheres to the inner wall of the chamber and is completely removed by the gas system. It is known that cleaning can be difficult.

JP 2004-031380 A US Pat. No. 7,204,913

Semiconductor International 2008/1 Jounal of Vacuum Science and Technoloby B24, 2191 (2006)

  However, the above-described prior art has not sufficiently considered the following problems.

  That is, in Patent Document 1, substances and particles that cause foreign substances are released from the coated film itself, and foreign substances may be generated, and it is necessary to optimize the conditions for coating the film. However, such a condition has not been taken into consideration in the present prior art.

  Further, as the degree of integration of semiconductor integrated circuits increases, long-term suppression of CD fluctuation is required. However, as described in Non-Patent Document 2, a metal material film is processed (generally called metal processing). ), If the material or the compound adheres to and remains on the wall surface of the processing chamber, the process performance may vary due to the remaining metal material in the subsequent processing in the processing chamber. Such fluctuation in process performance changes the result of processing of a film to be processed such as a semiconductor wafer, and the shape obtained as a result of processing as the number of processed sheets increases, so-called CD (Critical Dimension). , Critical dimension) will fluctuate.

  In order to solve such a problem, it is conceivable to perform a cleaning process for removing a residue or a process for suppressing fluctuations in process performance (for example, a seasoning process) for each wafer process. However, in an actual mass production site, there has been a problem that the overall throughput in the case of processing a predetermined number of lots is reduced by performing such specific processing. Such a point has not been taken into consideration in the prior art.

  An object of the present invention is to provide a plasma processing apparatus or a plasma processing method with little variation in shape obtained as a result of processing. It is another object of the present invention to provide a processing apparatus or a plasma processing method in which processing efficiency is improved and throughput is increased.

The present invention provides a plasma processing method for plasma-etching a material to be processed in a processing chamber, wherein a deposited film is formed by plasma using a mixed gas of SiCl ₄ gas and O ₂ gas or a mixed gas of SiCl ₄ gas and methane gas. After depositing the deposited film in the processing chamber, the surface of the deposited film is plasma etched using SF ₆ gas, and the surface of the deposited film is plasma etched, and then disposed in the processing chamber. After placing the material to be treated on a sample stage, placing the material to be treated on the sample stage, plasma-etching the material to be treated, plasma-etching the material to be treated, and then using NF ₃ gas And plasma cleaning the inside of the processing chamber.

It is a longitudinal cross-sectional view explaining the outline of a structure of the plasma processing apparatus which concerns on embodiment of this invention. FIG. 2 is a longitudinal sectional view schematically showing a structure of a film disposed on an upper surface of a semiconductor wafer that is a processing target material to be processed in the plasma processing apparatus according to the embodiment shown in FIG. 1. It is a graph which shows the elemental composition ratio of the deposit | attachment obtained when processing the film | membrane structure of Fig.2 (a). It is a characteristic which shows the change of the deposit film thickness deposited on the processing chamber inner wall surface after completion | finish of the etching of the film | membrane structure shown in FIG. 2 (b) is processed (Si-based) film containing Si as a component, C-containing film containing carbon as a component, and (SiO-based) film containing SiO as a component when the film structure shown in FIG. 2B is etched. It is a graph which shows the consumption amount of each of these coating films, when it coats on the wall surface of an indoor part. It is a graph which shows the Si2p spectrum which measured the surface of the coating film formed using the mixed gas of SiCl4 and O2 by XPS. It is a figure which shows the image obtained by measuring the coating film surface by SEM (Scanning electron microscopy). It is a figure which shows the image obtained by measuring the coating film surface by SEM (Scanning electron microscopy). It is a graph which shows the change of the number of the particle | grains liberated from the surface of a coating film at the time of changing the time which performs this post-processing (after treatment). It is a flowchart which shows the flow of a process of the semiconductor wafer implemented in the plasma processing apparatus which concerns on a present Example. 3 is a graph showing a change in an etching rate (rate) of a polysilicon (Poly-Si) film when a wafer having a film structure shown in FIG. It is a graph which shows the change of the etching rate of a polysilicon (Poly-Si) film | membrane with respect to the change of the time which continues a process, and the amount of Ti remaining in a chamber. It is a flowchart which shows the flow of a process including a metal cleaning step in the plasma processing apparatus shown in FIG. It is a flowchart which shows another example of the flow of a process including a metal cleaning step in the plasma processing apparatus shown in FIG. It is a graph which shows the change of the density | concentration of the metal component with respect to the depth position of the coating film in the modification shown in FIG. It is a graph which shows the time change of the emitted light intensity resulting from the metal component in the case where a metal film is etched in advance, and the case where it is not processed.

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

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a longitudinal sectional view for explaining the outline of the configuration of a plasma processing apparatus according to an embodiment of the present invention. In particular, in this embodiment, an etching apparatus using microwave ECR (Electron Cyclotron Resonance) is described.

  In this figure, in the plasma processing apparatus according to the embodiment, a plurality of introduction holes for introducing an etching gas into the vacuum vessel 101 are evenly arranged around the central portion in the upper portion of the vacuum vessel 101 whose upper portion is opened. A disc-shaped shower plate 102 (for example, made of quartz or yttria) and a dielectric window 103 (for example, made of quartz) are installed, and the inside of the processing chamber 104 having a substantially cylindrical shape in the vacuum vessel 101 is provided. Sealed by a dielectric window 103. A gas supply device 105 for flowing an etching gas is connected to the shower plate 102, and a space between the shower plate 102 and the dielectric window 103 above the shower plate 102 is connected from the gas supply device 105 via a pipe line and a passage, A processing gas is supplied into the processing chamber 104 through the introduction hole through this space.

  Further, below the vacuum vessel 101, a vacuum exhaust device (not shown) is connected and communicated via a vacuum exhaust port 106 disposed at the bottom of the substantially cylindrical space of the processing chamber 104 therein. On the other hand, in order to transmit electric power for generating plasma to the processing chamber 104, a waveguide 107 (or an antenna) that radiates electromagnetic waves is provided above the dielectric window 103.

  The electromagnetic wave transmitted to the waveguide 107 (or antenna) is oscillated by the electromagnetic wave generating power supply 109 and supplied to the inside of the waveguide 107. In the present embodiment, the frequency of the electromagnetic wave is not particularly limited, but in this embodiment, a microwave of 2.45 GHz is used.

  A magnetic field generating coil 110 that forms a magnetic field is disposed outside the vacuum chamber 101 on the outer peripheral side of the processing chamber 104, and is oscillated from an electromagnetic wave generating power source 109 to be guided to the waveguide 107 and the dielectric window 103. , The electric field introduced into the processing chamber 104 through the shower plate 102 causes an interaction with the magnetic field formed by the magnetic field generating coil 110 to dissociate the processing gas supplied into the processing chamber 104. Thus, plasma is generated in the processing chamber 104. Further, a wafer mounting which is a sample stage on which a disk-shaped semiconductor wafer 112 to be processed is placed on the upper surface of the circular shape in the lower part of the processing chamber 104 facing the disk-shaped shower plate 102. A placement electrode 111 is disposed.

  The wafer mounting electrode 111 has a substantially cylindrical shape, and the upper surface of the electrode is covered with a sprayed film (not shown) in which a ceramic material such as aluminum oxide or yttrium oxide is sprayed by spraying. Further, a film-like electrode made of a metal member is disposed inside the sprayed film (not shown), and this electrode is electrically connected to the DC power source 116 via the high frequency filter 115.

  Furthermore, a high frequency power source 114 is connected to the metal block disposed inside the wafer mounting electrode 111 via a matching circuit 113, and this block has an effect as a high frequency electrode. . Further, in the electrode block inside the wafer mounting electrode 111, a refrigerant flow path 117 is arranged which is arranged concentrically or spirally and through which the medium for temperature adjustment flows. The coolant channel 117 is connected to the temperature controller 118 via a pipe line disposed outside the wafer mounting electrode 111.

  In addition, a heater 119 is disposed in the upper part of the electrode block, and is connected to the heater controller 120. Further, a temperature sensor 121 is disposed on the wafer placement electrode 111, and the heater controller 120 is configured so that the temperature of the wafer placement electrode 111 and the wafer 112 is set to a desired temperature based on a signal output from the temperature sensor 121. And the operation of the temperature controller 118 for controlling the temperature of the refrigerant is adjusted.

  The wafer 112 is transferred into the processing chamber 104 by a transfer device such as a robot arm (not shown) and placed on the upper surface of the wafer mounting electrode 111, and then the wafer is mounted by the electrostatic force of the DC voltage applied from the DC power supply 116. It is adsorbed on the sprayed film on the electrode 111. At this time, a gas having a heat transfer property is supplied to the space between the back surface of the wafer 112 and the sprayed film, and the transfer of heat between the wafer 112 and the wafer mounting electrode 111 is promoted to thereby increase the wafer 112. The temperature of is adjusted.

  In this state, a desired processing gas, in this example, an etching gas, is supplied by the gas supply device 105, and then plasma is generated inside the processing chamber 104 while maintaining a predetermined pressure. Next, by applying a high frequency power from a high frequency power supply 114 connected to the wafer mounting electrode 111, a bias potential is formed above the sprayed film, and ions are drawn from the plasma into the wafer, whereby the wafer 112 is etched.

  Further, an emission spectrometer 123 for detecting light emission during the plasma processing is connected to the side wall portion of the vacuum vessel 101 constituting the inner wall of the processing chamber 104, and an output obtained from the emission spectrometer 123 is connected to this. The light emission data processing device 124 is transmitted, and the light emission data is numerically analyzed and detected using a calculator in the light emission data processing device 124.

FIG. 2 is a vertical cross-sectional view schematically showing the structure of a film disposed on the upper surface of a semiconductor wafer, which is a material to be processed, in the plasma processing apparatus of this embodiment. As shown in FIG. 2A, the structure of the film to be processed is formed on a substrate 207 as a base from above with a resist (Photo Resist, PR) (mask) 201 or a hard mask (carbon, SiO ₂ , SiN or A film using a material such as SiON or a film mainly composed of these is provided, a polysilicon (Poly-Si) film 203, and an oxide film 204 as an insulating film layer. Alternatively, as shown in FIG. 2B, a resist (Photo Resist, PR) (mask) 201 or a hard mask (carbon, SiO ₂ , SiN, or SiON) is used on the substrate 207 from the top, or these are used as main materials. ) 202, a polysilicon (Poly-Si) film 203, a metal (metal, for example, TiN) film 205, and a film (High-K film) 206 made of a high-k material (for example, HfO2).

  The type of metal, the number of stacked layers, and the thickness of the metal, the NMOS portion, and the PMOS portion are different. These film structures are required to be etched into a predetermined shape in order to form a semiconductor device circuit, particularly a gate or wiring structure.

  In this example, each film is processed by a different etching recipe. Further, the resist film 201 having a thickness corresponding to recent fine processing as a mask and etching resistance is insufficient only with the resist film 201 used in the past, which is made of an organic material, as the mask portion. The hard mask 201 made of a material such as amorphous carbon (ACL), SiN or SiON, and SiO2 or a laminated structure in which these are mixed is provided in the lower layer of the substrate. With such a hard mask 201, it is possible to etch the underlying poly-Si or metal material. Here, the description of the etching process of the mask 201 is omitted.

In this embodiment, the polysilicon film 203 is etched by using a gas containing chlorine (Cl) as a component (chlorine gas, eg Cl ₂ ) and a gas containing fluorine (F) as components (fluorine gas, eg CF 4). ) Or a mixed gas of Cl2 and HBr or the like is used as at least a part of the components. A gas such as O2 is also used as necessary.

  Next, in the etching process of the metal (for example, TiN) film 205 having the film structure shown in FIG. 2B, a relatively high wafer bias output is obtained in order to remove a natural oxide film or the like formed first at the metal layer interface. Increasing ions having high ion energy are incident, and the natural oxide film is removed mainly by the sputtering effect. As the processing gas used at this time, a gas containing HBr, Ar, or the like is used, but another gas system may be used.

After a natural oxide film is removed, a mixed gas of mainly Cl2 or Cl ₂ and HBr is used as the processing gas for etching the metal film 205. Since the metal film 205 of this embodiment is a thin film, the etching is performed by adjusting the wafer bias output so that the ion energy is relatively low.

Next, BCl ₃ or a mixed gas of BCl ₃ and Cl ₂ is used as a processing gas, and etching of the High-K (eg, HfO ₂ ) film 206 made of a high dielectric constant material is performed. In this step, good etching characteristics (shape, selection ratio) and the like are achieved by using low ion energy conditions.

  Next, details of the processing of the wafer to be processed according to the first embodiment of the present invention will be described with reference to FIGS. Here, the step of etching the film structure shown in FIG. 2A will be described. However, the film structure shown in FIG.

In this embodiment, in the etching of the film structure shown in FIG. 2A, when a material such as SiO ₂ or SiN is used as the mask 201, CxHyFz (x, y, z = 0, 1, 2,...) As a component, or such a gas, a diluent gas, and a gas such as oxygen. As described above, for the polysilicon film 203, a mixed gas of chlorine (Cl) -based gas (for example, Cl ₂ ) and fluorine (F) -based gas (for example, CF 4) or a mixed gas of Cl ₂ and HBr is used. A gas such as O ₂ is also used as necessary.

In order to measure the deposits deposited on the inner wall surface of the processing chamber 104 after performing each of these etching steps, the inventors installed a sample simulating the inner wall in the processing chamber 104 and placed the sample on the sample. The deposits deposited on the surface were measured by XPS (X-ray photoelectron spectroscopy). Although the inner wall of the processing chamber 104 used in this experiment is quartz, it has a composition similar to that of the reaction product generated in the etching process of the polysilicon film 203 in particular, so that the member constituting the reaction product and the inner wall is used. Al ₂ O ₃ was used as the sample in order to discriminate from the above materials.

In the experiment, CHF ₃ / SF ₆ is used as an etching step for the mask 202, Poly-BT (Break-Through) step is used as an etching step for the polysilicon film 203, and Cl ₂ / CF ₄ / Ar is used as a Poly-EndPoint and Poly- In the OE (Over-Etching) step, a gas containing Cl ₂ / HBr / O ₂ was used as a processing gas.

  FIG. 3 shows the composition ratio of elements detected on the sample after the processing of each step. FIG. 3 is a graph showing the composition ratio of the deposited elements obtained when the film structure of FIG. 2A is processed.

  As shown in this figure, the main components of the deposits formed on the inner wall of the processing chamber 104 are C and F in the mask 202 to Poly-BT steps. Since a peak is observed on the high energy side, CFx (x = 1, 2, 3) is considered to be the main composition. In addition, in the Poly-EndPoint to Poly-OE steps, Si and O are the main components of the deposit, and when the Si2p spectrum is observed, it has a peak in the vicinity of 103 eV, so it can be estimated that the SiOx film is formed.

In this experiment, the electron intensity obtained from Al on the sample surface (Al ₂ O ₃ ) was measured, and the CFx and SiOx densities of the deposited film were assumed to be predetermined values. The film thickness of the kimono can be determined. FIG. 4 shows the film thickness when SiOx is SiO ₂ and CFx is assumed to be similar to FTFE (Poly-tetra-fluoro-ethylene) and the density is 2.2 g / cm ³ . A CFx film is formed in the mask 201 to the Poly-BT step, and a SiOx film is formed in the Poly-EndPoint to Poly-OE step, but the step of switching from the CFx film to the SiOx film at the initial stage of etching (Poly-BT and Poly-EndPoint). It can be seen that the deposit film formed on the wall once disappears in this step. That is, it can be said that this period is easily affected when the wall surface of the processing chamber 104 is exposed and the inner wall state of the processing chamber 104 changes over time.

  In order to prevent the processing characteristics and results of the wafer 112 from being affected and fluctuated by such a change in the state of the inner wall of the processing chamber 104, the plasma in the processing chamber 104 is processed before the processing of the wafer 112. It is conceivable to coat the surface of the inner wall facing the surface with a film of a predetermined material. When etching a film having the above-described structure, the etching gas system to be used differs depending on the film type, and in some cases, the deposit film on the inner wall of the processing chamber 104 disappears as in the above example. Since the inner wall may be exposed, the film that covers the inner surface of the processing chamber 104 (hereinafter referred to as a coating film) is the film that is the target film when etching a plurality of films having the above film structure. It is desirable that it remains on the surface inside the processing chamber 104 until the end of this process, at least during the film switching step.

  For this reason, in this embodiment, a film thickness greater than the film thickness that is consumed during the etching process is deposited in advance. Further, in the etching process of the above-described film structure, plasma formed by supplying fluorine (F) -based or chlorine (Cl) -based gas as a processing gas is used. Therefore, the coating film is plasma resistant to such plasma. Must be high.

  FIG. 5 shows a Si structure as a component (Si-based) film, a carbon-containing film (C-based) film, and SiO as a component (SiO-based) when the film structure shown in FIG. 2B is etched. ) When the film is coated on the wall surface inside the processing chamber 104, the consumption amount of each of these coating films is a graph. In this figure, the coating film mainly composed of carbon (C) has a large consumption amount in a step (for example, in-situ ash step) using oxygen, and therefore, it is determined that the plasma resistance is low. On the other hand, since the consumption amount of Si or SiO-based coating film is relatively small and the plasma resistance is considered to be high, the inventors determined that Si or SiO-based film is suitable as a coating film. did.

In particular, in a coating film containing Si, the plasma resistance of a film containing Si and oxygen (O) and a film containing Si and carbon (C) are good. For example, a mixed gas of SiCl ₄ and O ₂ , or a mixed gas of SiCl ₄ and methane (CH ₂₎ is used as a gas species of a processing gas that forms plasma in order to attach such a coating film to the surface of a member in the processing chamber 104. The mixed gas of ₄ ) is preferred. A similar coating film can be formed by adding a dilution gas such as Ar.

FIG. 6 is a graph showing a Si2p spectrum obtained by measuring the surface of a coating film formed using a mixed gas of SiCl ₄ and O ₂ by XPS. In this figure, the result of analyzing the surface of quartz is also shown. Since both the coating film and quartz have a peak in the vicinity of substantially the same binding energy 103 eV, it can be seen that an oxide film (SiO ₂ ) is formed.

FIG. 7 is a view showing an image obtained by measuring the coating film surface by SEM (Scanning electron microscopy). The inventors have compared the surface of the coating film obtained by changing the conditions for forming the coating film, and as a result, when the O ₂ / SiCl 4 flow rate ratio is smaller than 0.5, the surface of the coating film is roughened. The knowledge that occurs is obtained. If such surface roughness of the coating film exists, problems such as non-uniformity of the inner wall coverage of the reactor due to non-uniformity of the coating film and generation of foreign matter due to the occurrence of cracks originating from the roughness may occur. . Therefore, in this embodiment, the flow rate ratio of O ₂ and SiCl ₄ is set to 0.5 or more in the processing gas introduced into the processing chamber 104 to form the coating film.

  The wafer 112 mounting surface on the upper surface of the wafer mounting electrode 111 is covered with a sprayed film, but during the plasma processing for forming the coating film, the same applies to the mounting surface when the wafer 112 is not mounted. A coating film is formed. For this reason, the coating film exists between the ESC film and the wafer while the wafer 112 is placed on the wafer mounting electrode 111 and a predetermined film having a film structure to be processed is being etched.

  According to the study by the inventors, at this time, the surface of the coating film immediately after being formed on the sprayed film has irregularities or surface roughness due to minute protrusions as shown in FIG. There is a non-uniform distribution. For example, the knowledge that such a convex part is a processus | protrusion by the material containing Si is acquired. Then, due to such unevenness and roughness, when the voltage is applied to the electrode of the thin film for electrostatic adsorption arranged in the sprayed film and a force is applied to the coating film between the wafer and the sprayed film, the above minute Cracks occur in the coating film starting from the roughness, and as the number of wafers processed increases, the material constituting the sprayed coating is released from the cracks as fragments, which again becomes the wafer 112 (another wafer). A problem that foreign matter is generated due to contamination.

  Such a problem may occur not only in the coating film on the surface of the wafer mounting electrode 111 but also in the film covering the surface of the member disposed inside the processing chamber 104. For example, when a plasma is formed in the processing chamber 104 and etching is performed on the product wafer 112 after the coating film is formed, the charged particles and reactive particles in the plasma interact with the material constituting the coating film. As a result, cracks and damages may occur, and as a result, free fragments may cause contamination and foreign matter as described above.

  If these foreign substances adhere to the wafer, the product yield may be reduced. In this embodiment, in order to suppress the occurrence of such a problem, after the coating film is formed in the processing chamber 104 by the plasma processing as described above in a state where the wafer 112 is not placed on the upper surface of the wafer mounting electrode 111, the protrusion Surface treatment to reduce unevenness and roughness. In this embodiment, such surface treatment is performed by performing predetermined etching on the surface of the coating film with plasma. By coating a film with resistance against plasma for etching treatment, after-treatment of such a film is performed, as shown in FIG. 8B, the roughness, protrusions, and irregularities on the surface of the coating film are reduced. The generation of the foreign matter can be suppressed.

  As a processing condition for performing the processing after being formed on such a coating film, processing using plasma using (F-based) gas containing fluorine as a component, for example, plasma using SF6 is effective. FIG. 9 shows the change in the number of particles released from the surface of the coating film when the time for performing this post-treatment (after-treatment) is changed.

  As shown in the figure, the number of particles is drastically reduced until the time for which the post-treatment using the plasma is continued is about 2 seconds, and the number is close to 0 after about 2 seconds. Asymptotically. The inventors have obtained such knowledge and recalled that the post-treatment using plasma for about 2 seconds or more reduces the surface roughness and defects of the coating film and suppresses the generation of foreign matter. Hereinafter, after the process of forming such a coating film in the processing chamber 104, the process of reducing surface roughness and defects using plasma is referred to as after-treatment.

  FIG. 10 is a flowchart showing the flow of processing of a semiconductor wafer performed in the plasma processing apparatus according to this embodiment. In this figure, a predetermined number of wafers stored in a container capable of storing wafers such as cassettes are handled as one lot, and members arranged in the processing chamber 104 in the plasma processing apparatus 100 for each lot. The example which starts from the aging process (step 1001) which makes the surface of this state suitable for a process is shown.

  In the aging process, in a state where the wafer 112 to be processed is not arranged in the processing chamber 104, an inert gas such as Ar is introduced to form plasma, and the surface of the member inside the processing chamber 104 is formed. In this process, the temperature, roughness, material, etc. are adjusted to a state suitable for the subsequent processing of the wafer 112. Thereafter, a cleaning gas is introduced into the processing chamber 104 to form plasma, and a cleaning process is performed to remove particles, coatings, and deposits remaining on the surface inside the processing chamber 104 (step 1002). ).

A coating process (step 1003) is performed in which the inner surface of the processing chamber 104 in a state where the cleaning process is performed and the cleaning process is performed is coated with a film for stabilizing the characteristics of the etching process. The coating process of this embodiment, as described above, as the gas species of the processing gas to form a plasma to deposit a coating film on the surface of the member in the process chamber 104, for example, mixed gas of SiCl4 and O ₂ Alternatively, a mixed gas of SiCl ₄ and methane (CH ₄ ) and a dilution gas are supplied together with Ar. By forming plasma using these gases, members disposed inside the processing chamber 104, for example, the surface of the inner side wall of the processing chamber 104 and the upper and side surfaces of the wafer mounting electrode 111 contain Si or SiO. It is covered with a coating composed of material.

This coating process (step 1003) is performed in a state where the wafer 112 for manufacturing the product to be processed is not placed on the placement surface of the wafer placement electrode 111. Thereafter, the introduced gas is changed, for example, switched to SF ₆ and introduced into the processing chamber 104 to form plasma. Etching is performed as a post-treatment (after treatment) for reducing roughness and defects on the surface of the coating film formed in the previous step by this plasma (step 1004).

  After step 1004, the processing gas is switched and the wafer 112 is transferred into the processing chamber 104 and placed on the mounting surface on the wafer mounting electrode 111 (step 1005). After the inside of the processing chamber 104 is hermetically sealed and sealed by a gate valve (not shown), as described above, a processing gas suitable for the film to be processed is introduced, and the film structure shown in FIG. 2 is etched. (Step 1006).

  When the processing of the film structure on the surface of the wafer 112 is completed, when the wafer 112 is carried out of the processing chamber 102 (step 1007), the control device (not shown) of the plasma processing apparatus 100 indicates whether there is a wafer 112 to be processed. Is obtained through the communication means, and it is determined whether or not to continue the processing target processing in the processing chamber 104 (step 1008). If it is determined that there is a wafer 112 to be processed next, the process returns to step 1002 to clean the deposit including the coating film, the film, and the remaining particles.

  If it is determined that there is no wafer 112 to be processed, the process proceeds to step 1009, and the processing chamber 104 is cleaned in the same manner as in step 1002, and then the processing of the wafer 112 is ended (step 1010). Even after the processing in the processing chamber 104 is completed, the processed wafer 112 may be in the process of being transferred, so that the control device determines that the wafer 112 has been stored in the original position of the original cassette. When this is done, the end of the process is notified from the control device by a notification means such as a display monitor, buzzer, or light provided in the plasma processing apparatus 100.

  By performing these processes shown in the present embodiment, the state of the inner wall of the processing chamber 104 changes with time as the number of processes increases or as the process progresses, so that adverse effects such as processing Generation of foreign matter from the inner wall of the chamber 104, deterioration in uniformity of the processing result of the wafer 112, and fluctuations in characteristics such as processing speed and processing shape reproducibility can be suppressed. Further, by performing the after-treatment process after forming the coating film, it is possible to suppress the damage of the surface of the coating film and the change of the state, thereby suppressing the generation of foreign matter and the influence on the processing of the wafer 112.

  Thereby, the reproducibility and yield of the etching process can be improved. Further, in this embodiment, the etching of the film structure as shown in FIG. 2A has been described. However, the invention included in this embodiment includes a metal film (for example, TiN) as shown in FIG. Even in the case of etching the film structure, the cleaning process shown in Step 1002 and Step 1008 can remove the component of the metal material remaining in the processing chamber 104, for example, a reaction product containing Ti as a composition together with the coating film. This makes it possible to perform plasma processing with good reproducibility.

  In the description of the embodiments so far, the process of manufacturing the semiconductor device by etching the film structure not including the metal film 205 shown in FIG. Next, a process of etching the film structure to be processed including the metal film 205 shown in FIG. A description of portions equivalent to those in the above-described embodiments is omitted.

  The technique for etching the film structure including the metal film 205 as shown in FIG. 2B is conventionally performed by cleaning the surface of the member inside the processing chamber 204 such as wet cleaning, and then performing the inside of the processing chamber 104. In order to adjust to a state suitable for the subsequent etching process of the wafer 112, a wafer having a film having no metal film such as Si, PR or oxide film on the surface thereof is disposed in the processing chamber 104 to form plasma. Then, the wafer for product manufacture was processed after the above-described process (seasoning process).

  FIG. 11 is a schematic diagram illustrating a process of processing a plurality of wafers in a predetermined lot having a film structure including a metal film / high-k film shown in FIG. It is a graph which shows the change of the etching rate (rate) of a silicon | silicone (Poly-Si) film | membrane. As shown in this figure, in the conventional technique, the etching rate increases rapidly at the very initial stage of the lot where wafer processing is started, and thereafter, the etching rate gradually approaches an arbitrary value and becomes stable.

  The inventors have found that such a phenomenon is caused by a gas supplied to the component (for example, Ti) of the metal film remaining in the processing chamber 104 such as fluorine (F) or chlorine (Cl) in the processing chamber 104. It was found that the concentration of F and Cl during the treatment increased due to the adsorption of these components. In general, the bond of Ti—F and Ti—O is stable, and conventionally, it has been difficult to remove under the cleaning treatment conditions using plasma. On the other hand, in order to suppress such process fluctuations, the same kind of wafer as the metal material (for example, TiN) contained in the material to be processed is processed, and Ti seasoning for attaching Ti to the inside of the processing chamber 104 is performed. It is also considered to stabilize the indoor atmosphere.

  FIG. 12 shows the conditions of the etching step of the High-K film 206 and the etching step of the metal (for example, TiN) film 205, for example, the etching rate of the polysilicon (Poly-Si) film 203 and the inside of the chamber with respect to the change of the processing time. It is a graph which shows the change of the amount of Ti which remains in. This figure shows that the amount of Ti is obtained by placing a clean Si wafer on the wafer mounting electrode 111 with Ti remaining inside the processing chamber 104 and supplying Ar as a plasma forming gas to form plasma. The amount of Ti deposited on the wafer as a result of sputtering Ti remaining on the inner wall surface of the processing chamber 104 was measured by TXRF (Total reflection x-ray fluorescence).

  The etching rate of the polysilicon film 203 decreases as the etching time of the High-K film 206 increases with respect to the etching time of the metal film 205, and the ratio of these times is a predetermined value. It can be seen that the etching rate gradually approaches an arbitrary value when the above is reached. Similarly, it has been found that the amount of Ti remaining in the processing chamber 104 also decreases as the ratio of the etching time of the High-K film 206 increases.

As described above, it is estimated that Ti remaining in the processing chamber 104 remains in a stable bonding state such as Ti—F or Ti—O. Therefore, in the step of etching the High-K film 206, the processing is performed. A gas containing BCl ₃ as a component is used as the gas. At this time, the inventors considered that B acts as a reducing agent, the bonds such as Ti—O and Ti—F are easily broken, and the remaining Ti is removed.

  That is, in the etching process of the film structure of the present embodiment, the metal component (for example, Ti) of the metal film 205 is supplied into the processing chamber 104 in the etching process step of the metal film 205, while the etching process of the High-K film is performed. In this step, the metal component (for example, Ti) remaining in the processing chamber 104 is removed. Each etching process has a different thickness depending on the structure of the semiconductor device to be manufactured, so that the amount of Ti remaining in the processing chamber 104 differs depending on the semiconductor device to be manufactured.

  In the case of manufacturing only a single semiconductor device, it is possible to stabilize the characteristics of the etching process for manufacturing the semiconductor device by stabilizing the surface state of the inner wall of the processing chamber 104 by the above-described technique such as Ti seasoning. Is possible. However, when a plurality of different devices are created at a time, it is necessary to reset the atmosphere (for example, wet processing) and seasoning for each product, resulting in a problem that the downtime of the apparatus becomes longer and the throughput is lowered.

  As described above, a metal, for example, a Ti-based reaction product remains in a strong bond of Ti—O, Ti—F, and the like, so that it is difficult to remove only by the conventional F-based gas plasma treatment. Therefore, as described in the above embodiment, before the wafer 112 to be processed is placed on the wafer mounting electrode 111 in the processing chamber 104, coating is performed on the inner wall of the processing chamber 104 and the sprayed film on the upper surface of the wafer mounting electrode 111. After performing the plasma treatment for forming the film, the wafer 112 is placed on the electrode and the film structure of the wafer 112 is etched. Then, after the etching process is completed, a cleaning process for removing the coating film is performed. At this time, a substance containing a component of the metal film 205 deposited on the coating film, for example, a Ti-based reaction product is removed together with the coating film. By performing such treatment, more stable plasma treatment is possible. However, depending on the treatment conditions and the like, a metal material such as a Ti-based reaction product may remain in the treatment chamber, and the remaining substance may cause This causes a problem that the etching process of the metal film 205 is affected and the characteristics of the process increase greatly.

  In this embodiment, in addition to the cleaning process after the formation of the coating film, a metal cleaning step for removing the components of the metal material remaining in the processing chamber 104 is provided. There are two cases for inserting such a metal cleaning step, and each case will be described below.

  The first case will be described with reference to FIG. FIG. 13 is a flowchart showing a flow of processing including a metal cleaning step in the plasma processing apparatus shown in FIG. In the present embodiment, an example is shown in which such processing is performed for each wafer, but the processing related to the operation may be performed for each predetermined number of wafers.

  FIG. 13 shows an operation when sealing the processing chamber after periodic maintenance such as replacement of parts inside the processing chamber 104 and starting depressurization to operate the plasma processing apparatus 100 again or when processing a new lot is started. Shows the flow. First, in this example, first, an aging process before a lot for adjusting the atmosphere inside the processing chamber 104 is performed (step 1301). Thereafter, a cleaning process for removing a normal reaction product is performed (step 1302). Such cleaning is performed by removing substances remaining on the inner wall surface of the processing chamber 104 by using plasma formed in the processing chamber 104.

  The aging process and the cleaning process are performed with the same purpose, condition, and action as those performed in Step 1001 and Step 1002 of FIG. The metal component may also be removed in this cleaning process (step 1302).

  Thereafter, a coating film is formed on the surface of the member inside the processing chamber 104 and the upper surface and side surface of the wafer mounting electrode 111 by the process of forming the above-described coating film having the same purpose, conditions, and action as in Step 1003 of FIG. (Step 1303). Next, a metal cleaning process for removing the metal material resulting from the component of the metal film 205 contained in the coating film is performed to remove the metal remaining in the processing chamber 104 (step 1304). Further, after that, a normal cleaning process equivalent to step 1302 is performed, and after the remaining coating film is removed (step 1305), the actual wafer 112 is processed.

  In this figure, before the wafer 112 to be processed is placed in the processing chamber 104 and the etching process of the wafer 112 is started, a coating film is formed on the wafer mounting electrode 111 having the inner wall of the processing chamber 104 and the sprayed film. Plasma treatment and after-treatment treatment for deposition are performed (step 1306). Thereafter, the wafer 112 is mounted on the wafer mounting electrode 111, and the film structure of FIG. 2B to be processed placed on the wafer 112 is subjected to an etching process by realizing a predetermined condition (step 1307).

  After the etching process on the film to be processed on the wafer 112 is completed, the wafer 112 is unloaded from the processing chamber 104 and then formed on the surface of the member inside the processing chamber 104 and the surface of the wafer mounting electrode 111 in step 1306. In the state where the coating film remains, a metal cleaning process for cleaning a component, for example, Ti, constituting the metal film 205 remaining in the processing chamber 104 is performed (step 1308).

  As described above, it is considered that Ti is often in a stable bonding state such as Ti—O or Ti—F. Therefore, in the metal cleaning process in Step 1308, the processing gas is contained in the processing chamber 104. As a component, a gas containing any one of boron (B), hydrogen (H), carbon (C), and silicon (Si), or a material composed of a combination thereof is supplied. Furthermore, any of these elements or a combination thereof and chlorine (Cl) or fluorine (F) are combined and supplied into the processing chamber 104 to form plasma, thereby forming Ti remaining in the processing chamber 104. Is removed.

As an example of the processing gas used in such a metal cleaning process, a mixed gas of HCl, SiCl ₄ , BCl ₃ , CH ₄ and Cl ₂ or F containing gas SF ₆ , CF 4, CxHyFz can be considered. In particular, according to the study by the inventors, a mixed gas of BCl ₃ and Cl _{2 and} a mixed gas of SiCl ₄ and Cl ₂ have a high Ti cleaning effect. Further, the same effect can be obtained by diluting the mixed gas with a diluent gas or the like as necessary.

In general, the mounting surface of the wafer mounting electrode 111 on which the wafer 112 is mounted is made of a ceramic material, and for example, a material such as Al ₂ O ₃ or Y ₂ O ₃ is generally used. . When the plasma faces a member made of such a ceramic material, the ceramic is etched and consumed due to the interaction with charged particles and reactive particles in the plasma. In this example, since the plasma treatment such as the after treatment treatment or the metal cleaning treatment can be performed in a state where the coating film is arranged on the placement surface made of ceramics, the above placement surface by plasma is used. Damage to the ceramics to be configured is suppressed.

The above metal cleaning process remains in the processing chamber 104 until it is combined with the coating film component or the component of the inner wall member of the processing chamber 104 and the amount of the metal component substance existing in the coating film is sufficiently reduced. After the execution, a cleaning process is performed to remove the coating film and other reaction products remaining in the processing chamber (step 1309). The cleaning process, when the coating film is a film composed of a component containing Si, for example, a coating film formed of plasma processing a mixed gas of a (step 1306) SiCl _4, O _2, or SiCl _4, O _2, When implemented using a mixed gas of Ar, cleaning is carried out by forming plasma using a gas containing fluorine (F) or containing fluorine (F) and oxygen (O) as components as a processing gas. .

This makes it possible to perform cleaning with a high cleaning effect. For example, SF ₆ , NF ₃ or a mixed gas of them and O ₂ are suitable. After this cleaning process, it is determined whether or not another wafer 112 is to be processed, and the process moves to step 1306 or step 1310 depending on the necessity of the process. In step 1310, it is determined that there is no wafer 112 to be processed next, and the processing in the processing chamber 104 is ended.

  By repeating the above plasma processing, the state of the surface of the member inside the processing chamber 104 is restored for each wafer and is adjusted to be suitable for the processing. It becomes possible. Also, by performing these processes, the variation in conditions inside the processing chamber 104 before and after periodic maintenance such as cleaning and replacement of parts inside the processing chamber 104 and between lots is suppressed, so that reproducibility is good. Processing is possible.

  Next, the second case will be described with reference to FIG. In this figure, description of the same parts as in the first case is omitted, and only different parts are described.

  FIG. 14 is a flowchart showing another example of a processing flow including a metal cleaning step in the plasma processing apparatus shown in FIG. In the second case, the timing for performing the metal cleaning process is different from that in the first case.

  In the first case, the metal cleaning process is performed after the etching process of the film structure to be processed of the wafer 112 is completed. In the second case, the coating film is applied to the member surface inside the processing chamber 104 and the wafer mounting. After being formed on the placement electrode 111, a metal cleaning process is performed before the wafer 112 is introduced into the processing chamber 104 and an etching process is performed (step 1404). In the second case, as in the first case, the state of the surface of the member inside the processing chamber 104 is restored and adjusted for each wafer 112, so that processing with good reproducibility and less foreign matter is realized. .

  Next, an example in which the effect of removing the metal component by the metal cleaning process is measured will be shown. FIG. 15 is a graph showing changes in the concentration of the metal component with respect to the depth position of the coating film in the modification shown in FIG.

In this measurement, the etching process of the metal film 205 having the film structure shown in FIG. 2B is performed on an arbitrary wafer 112, and Ti remains in the processing chamber 104. to simulate the conditions in which the coating film is deposited, the SiO2 film deposited by plasma treatment with a mixed gas of SiCl _4, O ₂ on the TiN film. The result of measuring the distribution of Ti inside from the surface of the coating film (SiO2 film in this example) by SIMS (Secondary ion mass spectrometry) is shown.

In the figure, the negative side of the X-axis indicates the SiO2 film, the positive side indicates the TiN film, and the Y-axis indicates the Ti concentration. From this figure, it can be seen that Ti is also present in the SiO ₂ film. This is because Ti in the processing chamber 104 diffuses into the SiO ₂ film, or Ti particles once etched and released inside the processing chamber 104 are deposited on the sample together with the SiO ₂ deposition. Conceivable.

As described above, the inventors present Ti as a metal component as a composition in the coating film (in this example, SiO ₂ film), so that the inside of the processing chamber 104 is formed by Ti remaining in the processing chamber 104. It was considered that there was a variation in the gas partial pressure, processing conditions, and characteristics over time. On the other hand, in order to reduce the influence of such residual Ti, it is considered that increasing the coating film thickness is also an effective means, but the time required for forming the coating film performed every wafer processing is also extended. As a result, there arises a problem that the throughput is lowered.

On the other hand, □ in the figure indicates the Ti distribution in the coating film when the plasma treatment with the mixed gas of BCl ₃ and Cl ₂ is performed as the metal cleaning treatment after forming the coating film. It can be seen that when the metal cleaning process is performed, the Ti concentration near the surface is reduced as compared with the case where the metal cleaning process is not performed. As described above, by performing the metal cleaning process, it is possible to reduce the concentration of Ti which is a metal component existing at the surface of the coating film and in the vicinity of the depth position thereof. As a result, the adverse effect on the atmosphere in the processing chamber 104 can be reduced by the metal component remaining in the coating film, for example, Ti, and plasma processing with high reproducibility, stability, and generation of foreign matter can be performed.

When a mixed gas of SiCl ₄ and Cl ₂ is used as a processing gas in the metal cleaning process, the effect of removing the metal component varies depending on the mixing ratio. For example, when the SiCl ₄ flow rate is increased with respect to the Cl ₂ flow rate, the residual amount of Ti tends to decrease. As a result of investigations by the inventors, it has been obtained by studying the inventors that the flow rate ratio of SiCl ₄ / Cl ₂ is 0.2 or more, thereby suppressing fluctuations in processing characteristics such as processing speed. On the other hand, if the flow rate of SiCl ₄ is further increased, a product containing excess Si as a component is deposited in the processing chamber 104. Therefore, when performing a cleaning process for a metal component (for example, Ti), a flow rate ratio of SiCl ₄ / Cl ₂ is used. Is preferably 0.2 to 1.0.

  In this embodiment, metal cleaning is performed until the amount of metal remaining in the processing chamber is sufficiently reduced. The end point of the metal cleaning process can be determined by detecting the light emission obtained from the plasma in the metal cleaning process.

  FIG. 16 is a graph showing temporal changes in emission intensity caused by the metal component in the metal cleaning process when the metal film is etched in advance and when it is not processed. In this measurement, TiN was processed as the material of the metal film 205, and the change in the emission intensity of Ti was measured. The dotted line in the figure indicates the emission intensity when the metal is not processed, and the solid line indicates the emission intensity when the metal is processed. When the metal film 205 is processed in advance, the emission intensity decreases with the continuation time of the cleaning process and decreases to the same level as when the metal is not processed.

  Therefore, the value of the emission intensity when the metal is not processed in advance is stored in a storage means such as a RAM, and the metal after processing the film structure including the set value and the metal film 205 with this value as a set value. The intensity of plasma emission obtained during the cleaning process is compared, and the end of the process can be determined using the time determined to be equal to the set value as the time to end the metal cleaning process.

  According to the above embodiment, the adverse effect on the processing due to the residue in the processing chamber 140 is reduced, and the partial pressure of the gas in the processing chamber 104 and the surface state of the internal members are stabilized. Thus, the variation of the shape as a result of the processing can be suppressed by suppressing the variation of the characteristics, and the processing accuracy can be improved.

  In the above-described embodiments and modifications, the plasma processing apparatus that uses ECR plasma has been described. However, the present invention is applicable to other plasma apparatuses such as inductively coupled plasma (ICP) and capacitively coupled plasma apparatus (CCP). The same effect can be obtained for the plasma treatment using.

DESCRIPTION OF SYMBOLS 101 Vacuum vessel 102 Shower plate 103 Dielectric window 104 Processing chamber 105 Gas supply apparatus 106 Vacuum exhaust port 107 Waveguide 108 Cavity resonator 109 Electromagnetic wave generation power source 110 Magnetic field generation coil 111 Wafer mounting electrode 112 Wafer 113 Matching circuit 114 High frequency Power source 115 Filter 116 DC power source 117 Refrigerant flow path 118 Temperature controller 119, 122 Heater 120 Heater controller 121 Temperature sensor 123 Emission spectrometer 124 Emission data processing device.

Claims (1)

In a plasma processing method of plasma etching a material to be processed in a processing chamber,
A deposition film is deposited in the processing chamber by plasma using a mixed gas of SiCl ₄ gas and O ₂ gas or a mixed gas of SiCl ₄ gas and methane gas;
After the deposited film is deposited in the processing chamber, the surface of the deposited film is plasma etched using SF ₆ gas,
After plasma etching the surface of the deposited film, the material to be processed is placed on a sample stage disposed in the processing chamber,
After placing the material to be processed on the sample stage, plasma-etching the material to be processed,
A plasma processing method comprising: plasma-etching the material to be processed and then plasma-cleaning the processing chamber using NF ₃ gas.

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