JP2007243020A - Plasma treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment device which performs stable microfabrication for a long period of time by covering an inner wall face of a treatment chamber with a material similar to a reaction product. <P>SOLUTION: The plasma treatment device is provided with: a vacuum treatment container; a sample stage 209 arranged inside the vacuum treatment container; a gas introduction means for introducing a process gas into the vacuum treatment container; a magnetic-field generation means for generating a magnetic field in the treatment container; and an exhaust means arranged at the lower part of the vacuum treatment container so as to exhaust a gas in the container. The plasma treatment device generates plasma by an interaction with the magnetic field while supplying high-frequency power into the vacuum treatment container so as to apply plasma treatment to a sample placed on the sample stage by the generated plasma. The vacuum treatment container is provided with: a tubular sidewall member 216, a lid member for covering the upper part of the sidewall member; and a dielectric plate 208 arranged on the sidewall member side of the lid member. A coating film including yttrium (Y) is formed onto the inner face of the sidewall member and the outer peripheral part of a face on the sidewall member side of the dielectric plate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus capable of suppressing damage to a wall surface of a processing chamber and performing stable fine processing over a long period of time.

  2. Description of the Related Art Plasma processing apparatuses such as plasma CVD and plasma etching apparatuses are widely used as semiconductor manufacturing apparatuses for manufacturing semiconductor devices by processing a workpiece such as a silicon wafer.

  In recent years, with the high integration of devices, circuit patterns are continually miniaturized, and the precision of processing dimensions required for these plasma processing apparatuses is becoming increasingly severe. In addition, with the diversification of device constituent materials, the etching recipe becomes complicated, and long-term mass production stabilization is an important issue.

  For example, in a plasma processing apparatus, a reactive gas plasma such as fluoride, chloride, bromide, etc. is used, so that the inner wall of the processing chamber is chemically and physically eroded, and as the number of wafers processed increases, reaction generation occurs. If an object adheres to the inner wall of the processing chamber, stable processing may not be possible for a long time.

  Further, the eroded processing chamber wall member and active radicals in the plasma may cause a chemical reaction and reattach as foreign matter to the processing chamber wall. The foreign matter reattached to the inner wall gradually increases in thickness by repeating the etching, and in the worst case, the foreign matter may fall off on the wafer and cause a product defect.

  In order to cope with such a problem, in the plasma processing apparatus, the surface of a member such as a processing chamber wall is subjected to anodizing treatment (so-called alumite treatment, a general thickness of 20 μm) that is stable against chemical reaction. I have been. Further, high-purity sintered alumina is often used for the stage on which the wafer is placed.

However, in recent years, the reduction of aluminum contamination has also become an important issue, and it is considered to use a plasma-resistant material other than alumite and alumina in order to continue the treatment stably over a long period of time. For example, by covering a processing chamber wall or stage of a plasma processing apparatus with a material mainly composed of Y ₂ O ₃ , Tb ₂ O ₃ , or YF ₃ , it is possible to perform stable treatment for a longer period of time. It is known that Such techniques are described in Patent Documents 1 and 2.
JP 2005-243987 A Japanese Patent Laid-Open No. 2005-243988

  The alumite used in the above prior art has insufficient plasma resistance for the purpose of guaranteeing stable treatment over a long period of time. In addition, the aluminum produced by cutting the anodized aluminum may contaminate the surface of the semiconductor wafer to be processed.

  The techniques disclosed in Patent Documents 1 and 2 are effective from the viewpoint of plasma resistance. However, no consideration is given to the place where the film is coated, and it cannot be said that the effect of the plasma-resistant material is sufficiently drawn out.

  For example, the prior art 1 shows that the entire processing chamber wall is coated with a plasma-resistant coating. Thus, it is effective from the viewpoint of plasma resistance to coat the entire processing chamber with a plasma-resistant coating. However, when the entire processing chamber is covered with a plasma-resistant film, it is impossible to determine the end point at the time of wafer processing because light emitted from plasma cannot be collected for processing the wafer. On the other hand, if the quartz member constituting the processing chamber is used without being coated with a plasma-resistant material, a change with time occurs in that the etching rate varies as the number of wafers processed increases. For this reason, it becomes difficult to continue stable processing for a long time.

  The present invention has been made in view of these problems, and provides a plasma processing apparatus capable of microfabrication stable over a long period of time by coating a part of a processing chamber wall surface with a material equivalent to a reaction product adhering thereto. To do.

  In order to solve the above problems, the present invention employs the following means.

  A vacuum processing container, a sample stage arranged in the vacuum processing container, a gas introducing means for introducing a process gas into the vacuum processing container, a magnetic field generating means for generating a magnetic field in the processing container, and a lower part of the vacuum processing container And an evacuation means for evacuating the gas in the container, supplying high-frequency power into the vacuum processing container to generate plasma by interaction with the magnetic field, and placing the plasma on the sample stage by the generated plasma In the plasma processing apparatus for performing plasma processing on the sample, the vacuum processing container includes a cylindrical side wall member, a lid member that covers an upper portion of the side wall member, and a dielectric plate disposed on the side wall member side of the lid member. The outer peripheral portion of the inner surface of the side wall member and the surface of the dielectric plate on the side wall member side formed a film containing yttrium (Y).

  Since the present invention has the above-described configuration, it is possible to provide a plasma processing apparatus capable of performing stable microfabrication over a long period of time.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings. FIG. 1 is a schematic plan view for explaining the overall configuration of a vacuum processing apparatus used in the present embodiment.

  In FIG. 1, the vacuum processing apparatus main body 100 can be divided into two blocks. That is, the atmosphere side block 101 is disposed in front of the apparatus main body 100 (downward in the drawing). A wafer supplied to the apparatus main body 100 from the outside is transferred to the processing block 102 via the atmosphere side block 101.

  The processing block 102 is disposed behind the apparatus main body 100 (upward in the drawing). The processing block 102 includes processing units 103, 103 ′ and 104, 104 ′ having vacuum processing chambers for processing wafers in a reduced pressure environment, a transfer unit 105 for transferring wafers to these processing chambers under reduced pressure, and A plurality of lock chambers 113, 113 ′ connecting the transfer unit 105 and the atmosphere side block 101 are provided. These units are units that can be decompressed and maintained at a high degree of vacuum. That is, the processing block 102 is a vacuum block.

  On the other hand, the atmosphere side block 101 has a casing 108 provided with a transfer robot (not shown) inside, and a wafer cassette 109 and a dummy cassette 110 are attached to the casing 108. Wafer cassette 109 stores processing or cleaning wafers, and dummy cassette 110 stores dummy wafers.

  The transfer robot in the housing 108 loads or unloads wafers between the cassettes 109 and 110 and the lock chamber units 113 and 113 '. In addition, the atmosphere side block 101 includes an alignment unit 111 on the housing 108. The transfer robot can change the posture of the transferred wafer by using the alignment unit 111. Thereby, the posture of the wafer after transfer in the cassettes 109 and 110 or the lock chamber units 113 and 113 'can be set to a desired posture.

  In the processing units 103, 103 ′ and 104, 104 ′ constituting the processing block 102 in this embodiment, the processing units 103, 103 ′ are etching processing units, and the processing units 104, 104 ′ are ashing processing units. .

  Further, the processing block 102 includes control units 107 and 107 ′ including a flow rate adjusting device (Mass Flow Controller) that adjusts the supply of a fluid such as a gas or a liquid necessary for the unit constituting the processing block 102 or the processing chamber. These units are arranged below the processing units 103 and 103 ′.

  As described above, the processing units 103, 103 ′ and 104, 104 ′ are an etching processing unit and an ashing processing unit, respectively, and these units are connected to each side of the polygon of the transfer unit 105 having a polygonal plane. Has been. Further, lock chambers 113 and 113 ′ are connected to the remaining side of the transport unit 105.

  In this embodiment, the processing units 103, 103 ′ and 104, 104 ′ connected to the transport unit 105 are detachably connected to the transport unit 105. Further, the transport unit 105 is detachably connected to the lock chambers 113 and 113 '.

  Next, the configuration of the processing unit (plasma processing apparatus) shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a longitudinal sectional view for explaining the configuration of the etching processing unit shown in FIG.

  As shown in FIG. 2, a discharge chamber 210 is disposed at the top of the processing unit 200, and the discharge chamber is disposed inside the lid member 201 that forms a lid of the vacuum vessel. Antenna 202, a magnetic field generator 203 disposed on the side and above the antenna 202 and surrounding the discharge chamber, and a ceiling member disposed below the antenna 202. ing. Further, a high frequency power supply unit 205 that supplies power of a UHF band frequency of 300 MHz to 1 GHz emitted from the antenna 202 is disposed above the magnetic field generation unit 203. In this embodiment, the frequency of the power supply unit 205 is set to 450 MHz. . The antenna 202 is disposed inside a lid member 201 made of a conductive member such as SUS. The antenna 202 and the lid member 201 are insulated from each other and emitted from the antenna 202. A dielectric 206 that conducts electromagnetic waves to the lower ceiling member side is disposed.

   The ceiling member includes a quartz plate 207 made of a dielectric material such as quartz covering the upper surface of the processing chamber in the vacuum vessel in order to conduct the transmitted electromagnetic wave to the lower processing chamber side, and the quartz plate 207. And a shower plate 208 having a plurality of holes formed therein for dispersing and introducing the supplied processing process gas into the processing chamber. The shower plate 208 is a disc that is integrally formed of an insulating material and has an outer peripheral portion supported.

  The space formed above the sample stage 209 below the shower plate 208 is an electromagnetic wave from the antenna 202 introduced into the supplied process gas through the quartz plate 208, and the magnetic field supplied from the magnetic field generator 203. The discharge chamber 210 forms a plasma by the interaction of these. In addition, a minute space is formed between the quartz plate 207 and the shower plate 208, and the process gas is first supplied to this space and flows into the discharge chamber 210 through the hole of the shower plate. This space is a buffer chamber 211 provided so that the process gas is dispersed from the plurality of holes and flows into the discharge chamber 210. The process gas is supplied from a controller 214 that adjusts the flow rate, and is supplied to the processing unit 103 through a process gas line 212 and a process gas shut-off valve 213.

  In this manner, the process gas can be dispersed and introduced into the discharge chamber 210 from the plurality of holes. These holes are mainly arranged at positions facing the position on the sample stage 209 where the sample is placed, and cooperate with the buffer chamber 211 that disperses the gas so as to be uniform. The density can be made more uniform.

  A lower ring 215 is disposed below the lid member 201 on the outer peripheral side of the quartz plate 207 and the shower plate 208, and a gas line through which the process gas flows into the buffer chamber 211 is disposed inside the lower ring 215. A gas passage communicating with 212 is provided.

  Further, below the shower plate 208, a discharge chamber side wall member 216 that partitions the discharge chamber 210 facing the plasma inside the vacuum vessel is provided. On the outer peripheral side of the inner wall member 216, there is provided a discharge chamber outer wall member 217 disposed so as to surround the inner wall member 216. The outer wall surface of the inner wall member 216 and the inner wall surface of the outer wall member 217 of the discharge chamber are provided. Are in contact with each other. In the present embodiment, the inner wall member 216 and the outer wall member 217 each have a substantially cylindrical shape and are configured to be substantially concentric. A heater is wound around the outer peripheral surface of the outer wall member 217, and the temperature of the inner wall member 216 in contact with the outer wall member 217 is adjusted by adjusting the temperature of the outer wall member 217.

  On the outer peripheral side of the outer wall member 217, a discharge chamber base plate 218 that is in contact with the lower surface thereof is disposed. The lower surface of the discharge chamber base plate 218 is connected to a vacuum chamber portion disposed below the discharge chamber base plate 218. The inner wall member 216 is also a member that acts as a ground electrode for the sample stage 209 serving as plasma and electrodes in the discharge chamber 210, and has an area necessary for stabilizing the plasma potential. . The inner wall member 216 needs to ensure sufficient thermal conductivity and conductivity between the outer wall member 217 and the lid member 201 that are connected in contact with each other because of the action as the ground electrode.

  Note that the inner wall member 216, the outer wall member 217, and the lid member 201 are all made of a conductive member, and are exposed to the atmosphere side outside the processing unit 200, so that wiring for grounding can be easily connected. It is comprised so that.

  One or more chambers are arranged inside the outer chambers 219 and 220 constituting the outer wall of the vacuum processing chamber in the processing unit 200. That is, one is a multiple chamber arranged inside the other. In this embodiment, it has two chambers inside and outside. That is, the inner chamber 221 is provided inside the upper outer chamber 219, and the inner chamber 222 is provided inside the lower outer chamber 220. That is, two upper and lower inner chambers 221 and 222 are provided. The sample stage 209 is disposed inside the inner chambers 221 and 222, and the inside of the innermost chamber constitutes a vacuum processing chamber 223 in which plasma is formed and gas and reaction products flow and are exhausted.

  In addition, the inner chambers 221 and 222 have conductivity, and are electrically connected to the outer chambers 219 and 220 so as to have a predetermined potential. The inner chambers 221 and 222 face the plasma inside as described above, and need to be set to a specific potential in order to stabilize the process or to stabilize the interaction with the particles in the plasma. There is. In the present embodiment, the inner chambers 221 and 222 are set to the ground potential. Thereby, like the discharge chamber side wall member 216, the potential of the plasma is stabilized and the interaction is stabilized.

  In this embodiment, the temperature of the surface of the wall constituting the vacuum chamber is adjusted to adjust the interaction between the surface and the plasma, particles contained therein, gas, and reaction product. As described above, by appropriately adjusting the interaction between the plasma and the wall surface of the vacuum chamber facing the plasma, the plasma characteristics such as plasma density and composition can be brought into a desired state. Further, in the configuration of the present embodiment, there is a space between the inner chamber 219 and the outer chamber 220 constituting the vacuum chamber part that is decompressed by the exhaust means and maintained at a high degree of vacuum. For this reason, a device is required to adjust the temperature of the inner chamber 219 constituting the vacuum chamber 223.

  The sample stage 209 is generally called an electrostatic adsorption electrode. The sample stage 209 that is an electrostatic chucking electrode includes an electrostatic chucking electrode 234 made of aluminum, a dielectric film 235, and an electrode cover 236. Although not shown, a flow path through which the refrigerant circulates is formed in the electrostatic adsorption electrode 234, and the refrigerant adjusted to a predetermined temperature by the temperature control unit is supplied. The temperature of the refrigerant is about −10 to 60 ° C.

  The electrode cover 236 is a cover for protecting the dielectric film 235 which is a substantially circular surface on which the semiconductor wafer is placed. The electrode cover 236 is disposed so as to surround the outer peripheral side wall of the dielectric film 235 which is a wafer mounting surface, and is placed on the outer peripheral portion of the upper surface of the sample table 209. As the material, insulators such as alumina and quartz, ceramics, silicon compounds, and the like are used. In addition, the size of the sample stage 209 is 340 mm in diameter and 40 mm in total thickness when a 12-inch (300 mm diameter) semiconductor wafer is targeted. A high voltage power source 237 for electrostatic attraction and a bias power source 238 for supplying bias power in the range of 200 kHz to 13.56 MHz, for example, are connected to the electrostatic attraction electrode 234 via a matching circuit 239. In the present embodiment, the frequency of the bias power source 238 is 2 MHz. The dielectric film 235 is provided with linear slits extending radially and a plurality of concentric slits communicating with the slits, and heat transfer from the gas introduction holes opened in communication therewith. He gas is introduced, and the back surface of the wafer is filled with a uniform pressure of He gas (usually about 1000 Pa) through the slit.

  The dielectric film shown in the present embodiment is made of alumina ceramics formed by a thermal spraying method having a thickness of 0.1 mm. The material and thickness of the dielectric film 235 are not limited to this example. For example, in the case of a synthetic resin, a thickness of 0.1 mm to several mm can be selected. In addition, a thin film electrode to which a voltage for adsorbing and holding the semiconductor wafer to be processed on the dielectric film 235 (sample stage 209) is provided is provided inside the dielectric film 235. ing.

  In the present embodiment, a medium passage (not shown) through which a heat exchange medium flows is arranged inside the discharge chamber base plate 218, and a heat exchange medium such as water is circulated through the medium passage. The temperature of the discharge chamber base plate 218 is adjusted, whereby the temperature of the inner chamber 221 is adjusted via a member that is disposed between the discharge chamber base plate 218 and the members of the inner chamber 221 and connects them. That is, the discharge chamber base plate 218 and the side wall member of the inner chamber 221 are thermally connected, and heat is conducted between the two to exchange heat. If heat exchange is possible through heat conduction, another member may be disposed between them.

  In order to place the sample to be processed on the sample stage 209 in the inner chambers 221 and 222, a gate capable of transporting the wafer into the inner chamber 221 or 222 is required. Further, a valve that opens and closes the gate to cut off and communicate the space inside and outside the chamber is required.

  In this embodiment, the gate provided between the inside of the processing unit 200 and the inside of the transfer unit 105 is opened or closed to open or close them, and the atmosphere gate valve 224 that connects and blocks both, and the inside and outside of the inside chamber 221. And a process gate valve 225 for connecting and blocking the two by opening or closing.

  The atmospheric gate valve 224 is arranged on the inner side wall of the transport unit 105 and is configured to be movable in the vertical and horizontal directions by the driving means 226, and is closed or opened so as to seal the gate on the inner side wall. . The outer chamber 219 constituting the vacuum container is provided with the process gate at a position where it communicates with the gate on the transport unit 105 side when the transport unit 105 is connected.

  A process gate valve 225 for opening, closing and sealing the process gate is disposed in a space between the outer chamber 219 and the inner chamber 221. The process gate valve 225 is configured to be movable in the vertical and horizontal directions by the driving means 227 below the process gate valve 225. The process gate valve 225 is disposed on the side wall of the inner chamber 221 when closed and closes the gate on the inner side wall. In this state, the inner surface of the inner chamber 221 has a substantially cylindrical shape with no irregularities. In other words, the central part of the valve body of the process gate valve 225 is provided with a convex part that allows the inner surface of the inner chamber 221 to have a substantially cylindrical shape with no irregularities.

  The process gate is arranged in a position and a shape that do not contact the wafer and the robot arm when the robot arm in the transfer chamber for transferring the wafer transfers the wafer.

  In the present embodiment, two upper and lower inner chambers are provided, and are arranged separately at 221 and 222 above and below the block of the sample stage 209. That is, the block of the sample stage 209 is disposed below the inner chamber 221. The block of the sample table 209 includes a sample table (main body) 209 and support beams 228 that support the sample table 209 and are arranged around the axis with the sample table 209 as a central axis. In the present embodiment, the inner chamber 221 and the outer chamber 219 and the sample table main body 209 have a substantially cylindrical shape, and the gas in the space on the sample table 209 in the inner chamber 221 is a space between the support beams. Flows downward through the space in the inner chamber 221.

  The support beam 228 holds the sample table 209 in the inner chamber 221 via a ring-shaped support base member 229 arranged around the sample table 209. In the support base member 229, the support beam 228, and the suspension beam 230, a pipe and a power line for supplying gas and refrigerant to the sample table 209 are disposed. The sample table 209, the support beam 228, and the support base 229 can be lifted out of the outer chamber 219 by being lifted as an integral block. Maintenance or replacement of the sample stage 209 is less frequent than maintenance of the inner chamber 221. For this reason, it is possible to improve the efficiency of the maintenance work of the apparatus by adopting a structure that can move integrally as a block.

   A lower inner chamber 222 is disposed below the block of the sample table 209, and an opening is disposed in a central portion of the inner chamber 222. This opening communicates with an exhaust means having an exhaust valve 231 and an exhaust pump 232 disposed below the inner stage 222 and below the sample stage 209, and the inner chamber 221 flowing around the sample stage 209. This is the part through which the gas flows. That is, the space between the support beams 228 around the sample stage 209 and the space in the inner chamber 222 below the sample stage 209 are exhausted by the processing gas in the processing unit 200, particles in the plasma, and reaction product particles flowing. It is an exhaust route.

   The exhaust valve 231 that is an exhaust means of the processing unit 200 includes a plurality of plate-shaped shutters that can communicate or block between the exhaust pump 232 disposed below and the space inside the inner chamber 222. The exhaust gas flow rate and speed can be adjusted by rotating the shutter and adjusting the open exhaust passage area. Thus, in the present embodiment, the exhaust means is disposed below the sample stage 209, particularly directly below. Plasma, processing gas, and reaction products in the space above the sample stage 209 in the inner chamber 221 are exhausted to the exhaust valve 231 through the space around the sample stage 209 and the space in the inner chamber 222 below the sample stage 209. Flowing the route. Thereby, the processing unit 200 can achieve a vacuum of a pressure of 1/10000 Pa by the exhaust pump 232.

   In addition, as shown in FIG. 2, the exhaust gate plate 233 is formed on the lower surface of the sample table 209 and the support beam 228 by a pusher (not shown) when plasma is generated to process the sample. Can be lifted until close or touching. Thereby, it is possible to suppress the flow of plasma, process gas remaining, reaction products, and the like in the processing chamber exhausted along with the processing of the sample from being inhibited by the exhaust gate plate 233, and exhaust efficiency is improved. In addition, the space required for stabilizing the disturbed and disturbed exhaust flow in the vacuum chamber 223 below the support beam 228 and the sample stage 209 is suppressed, and the processing chamber portion is further downsized to reduce the exhaust time. It is possible to shorten the process and to improve the processing efficiency. Further, in the above configuration, it is possible to suppress the particles from adhering to the exhaust gate plate 233. As a result, maintenance intervals such as replacement of the exhaust gate plate 233 and removal of deposits can be extended.

   Further, an evacuation unit is disposed below the sample stage, particularly directly below, to suppress bending of the exhaust path of particles in the processing chamber such as plasma. As a result, the exhaust speed is improved, the working time is shortened, and the operating efficiency of the apparatus main body is improved. Furthermore, an exhaust valve having a plurality of shutters is provided below the sample stage. For this reason, the exhaust buffer space under the sample stage is reduced, and the exhaust time can be further reduced.

   Further, the support beam of the sample table is arranged on a substantially axial object with the sample table as the center, so that the exhaust path can be made more perpendicular to the exhaust means below the sample table. Further, it is possible to suppress the occurrence of a difference in the length of the exhaust path passing through the periphery of the sample stage, and to make the flow of particles such as plasma in the processing chamber uniform. Also, the density of particles above the wafer on the sample stage can be made more uniform, and the wafer processing can be stabilized.

  Next, a process when performing an etching process on silicon using the plasma processing apparatus according to the present embodiment will be described.

  FIG. 3 is an enlarged view of the vicinity of the processing chamber of the etching processing unit (plasma processing apparatus) shown in FIG. First, the semiconductor wafer W, which is an object to be processed, is loaded into the processing unit 200 by the transfer unit 105, and then placed on the electrostatic chucking electrode 234 of the sample stage 209 and sucked. Next, gases necessary for etching the semiconductor wafer W, such as a plurality of types of gases including halogen, are supplied from the process gas line 212 into the processing unit 200 with a predetermined flow rate ratio. At the same time, the processing unit 200 is adjusted to a predetermined processing pressure by the exhaust pump 232 and the exhaust valve 231.

  Next, high frequency power in the UHF band such as 450 MHz is supplied from the high frequency power supply unit 205 to the antenna 202, and electromagnetic waves are radiated from the antenna 202. Then, the interaction between the electromagnetic wave and a substantially horizontal magnetic field of 160 gauss (electron cyclotron resonance magnetic field intensity with respect to 450 MHz) formed inside the processing unit 200 by the magnetic field generation unit 203 generates plasma P in the processing unit 200. Generate. Thereby, the process gas is dissociated to generate ions and radicals. Further, by adjusting a bias power source 238 that supplies bias power to the electrostatic adsorption electrode 234, the composition ratio of ions and radicals in the plasma or incident energy is controlled, and further, the temperature of the semiconductor wafer W is controlled. Etching is performed.

  A multilayer film is formed on a wafer which is an object to be etched. Therefore, during etching, the process gas type, pressure, high-frequency power source output, magnetic field generator current, and bias power are adjusted to values suitable for the film quality. Thus, different processing conditions are set for each film in order to optimize the etching shape. Further, a single film may be processed by combining several processing conditions. In the present embodiment, a single wafer is processed in combination with about 4 to 8 processing conditions.

  As described above, in the etching processing apparatus, the process gas introduced into the processing chamber is efficiently turned into plasma by the interaction between the high-frequency electric field and the magnetic field of the magnetic field coil. In the etching process, a desired etching shape can be obtained by controlling the incident energy of ions in the plasma incident on the wafer by a high frequency bias.

   In order to obtain a desired shape, it is necessary to stop the etching process at a desired time. During the etching process, it is possible to fix the processing time, but as described above, since the multilayer film is formed on the wafer, the end point detection system detects the end point of the process and stops the process. It is desirable to do.

  There are various methods for the end point detection system. In the present embodiment, only a specific light emission wavelength of the plasma is monitored and the end point is determined by a change in the specific light emission wavelength, or the optical fiber 303 above the quartz plate. And adopting a method of determining the end point by interference light obtained from the wafer surface.

In the plasma processing apparatus shown in this embodiment, magnetic field lines 301 as shown in FIG. For this reason, high-density plasma is generated immediately below the shower plate 208 by the high frequency and the magnetic force lines 301 applied from the antenna 202. Further, the generated plasma P is constrained by the magnetic field lines 301. For this reason, the plasma density on the surface of the inner wall member 216 covered with Y ₂ O ₃ spraying on the extension of the magnetic field lines 301 is increased. In particular, the plasma density increases in the vicinity of the outer peripheral surfaces of the shower plate 208 and the inner wall member 216 and the upper end of the inner wall member being in contact with the shower plate where the strength of the high frequency or magnetic force lines 301 is large.
At this time, an electric circuit is formed through the bias power source 238 for supplying bias power, the electrostatic adsorption electrode 234, the plasma P, and the surface of the inner wall member 216. In this circuit, the surface of the inner wall member 216 having a high plasma density is a ground plane. For this reason, electrons in the plasma move at a high speed to the surface of the inner wall member 216 that is the ground plane, and an ion sheath (electric field) is stably generated by the remaining ions. In particular, since the ions in the plasma are incident on the inner wall member upper side 302 due to the large thickness of the ion sheath, the inner wall member upper side 302 is significantly eroded. In addition to ion incidence, corrosion by active radicals in the plasma also occurs.

  Next, changes with time of the plasma processing apparatus in the present embodiment will be described. In the plasma processing apparatus shown in the present embodiment, a phenomenon in which the etching rate gradually increases as the number of wafers processed increases, a phenomenon in which the etching shape gradually decreases, or a phenomenon in which foreign matters gradually increase occurs. As described above, since a multilayer film is formed on the wafer, the processing conditions differ for each film. Further, in order to optimize the etching shape, each film is processed by combining several processing conditions. Among these, the treatment conditions with the greatest change over time were the conditions for treating Poly-Si first. The gas (process gas) to be used is a fluorine-based gas containing carbon and a fluorine-based gas containing sulfur.

  4A and 4B are diagrams for explaining the change over time in the processing conditions. FIG. 4A is a view showing the change over time in the etching rate, and FIG. 4B is a view showing the change in the number of foreign matters on the wafer surface. As shown in FIG. 4A, the etching rate monotonously increases as the number of wafers processed increases. FIG. 4A also shows an etching shape (completed dimension). As shown in the figure, it can be seen that the etching shape (completed dimension) is narrowed by increasing the etching rate.

  In the etching shape process, the end point is determined based on the change point of the etching conditions. However, there is also a phenomenon that the end point determination time based on the above conditions gradually becomes faster as the number of processed sheets increases. For this reason, it is considered that there is a correlation between the etching shape (complete dimension) and the etching rate.

  In addition, as shown in FIG. 4B, the number of foreign matters increases with the number of wafers processed. That is, it is considered that the reaction product generated by the etching adheres to the inner wall of the vacuum vessel, and the attached product is sequentially deposited to become a foreign substance.

  FIG. 5 is a diagram for explaining the adhesion state of the reaction product. FIG. 5A shows the state of adhesion of reaction products on the shower plate 208. The reaction product was particularly thickly deposited on the outer peripheral portion 501 of the shower plate 208 (in the range of about 5 to 10 mm from the outermost periphery). Moreover, in the intermediate part 502 of the range of about 10-30 mm from the outer peripheral part, it was deposited thinly as it approached the shower plate center. Further, in the central portion 503 (30 mm to the center of the shower plate), the reaction product is not attached because it is etched by plasma. Thus, a lot of adhesion is detected on the outer peripheral end side of the upper portion of the substantially cylindrical discharge chamber 210. The upper corner of the discharge chamber 210 is a region where the intensity of the electromagnetic field is large and the plasma density is large.

  FIG. 5B is a diagram for explaining the adhesion state of the reaction product on the electrode cover. As shown in the figure, in the electrode cover 236, the reaction product was thinly attached to the electrode cover upper surface 504. Note that no particularly noticeable adhesion was observed on the inner wall member 216.

  Next, in order to know what elements are contained in the reaction product, component analysis of these deposits was performed.

FIG. 6 is a diagram showing the result of component analysis, FIG. 6 (A) is a diagram showing the analysis result of the reaction product on the shower plate, and FIG. 6 (B) is a diagram showing the analysis result of the reaction product on the electrode cover. As shown in FIGS. 6A and 6B, elements Y, F, O, and C were detected from the reaction products deposited on the shower plate 208 and the electrode cover 236. However, since C uses a tape at the time of measurement, there is a possibility that C contained in the tape is detected. Considering the above, it can be considered that Y ₂ O ₃ , YF ₃ or a CF-based reaction product adheres to the inner wall of the vacuum vessel.

  Further, in an apparatus in which the number of wafers to be processed is overlapped, when only the quartz member (shower plate 208, electrode cover 236) is replaced with a cleaned part and the etching rate is measured, the etching rate is higher than that of parts having a number of processed wafers. It decreased by 4 nm / min.

On the other hand, the quartz member is overlaid with wafer processing, and the inner wall member 216, inner chamber 221 and process gate valve 225 covered with the Y ₂ O ₃ sprayed film are replaced with cleaned parts to change the etching rate. When measured, the etching rate decreased by 2 nm / min.

From these facts, it is understood that the etching rate is influenced not only by the deposition of the reaction product on the quartz part but also by the deposition of the reaction product on the part coated with the Y ₂ O ₃ sprayed film.

 Similarly, a separation test for quartz parts was also performed. That is, when the etching rate was measured by replacing only the shower plate 208 with the cleaned parts in the state of the apparatus in which the number of wafers to be processed was overlapped, it decreased by 6 nm / min as compared with the parts that had been processed. Similarly, when only the electrode cover 236 was replaced with a cleaned part, the etching rate decreased by 4 nm / min. That is, it has been found that the shower plate 208 has a greater influence on the etching rate than the electrode cover 236.

Summarizing the above measurement results, it is considered that the member covered with the shower plate: electrode cover: Y ₂ O ₃ sprayed film has an influence at a ratio of 6: 4: 5.

In addition, when the change of the etching rate at the time of using the electrode cover 236 made of a Y ₂ O ₃ sintered body as the electrode cover 236 is measured, the electrode cover is changed to a cleaned part as compared with the parts overlaid with the wafer processing. In the case of replacement, the etching rate decreased by 0.7 nm / min. That is, it was found that the variation in the etching rate when using the electrode cover 236 made of a Y ₂ O ₃ sintered body was low.

  FIG. 7 is a diagram for explaining a mechanism for attaching a reaction product. As shown in FIG. As described above, in the plasma processing apparatus using the UHF band electromagnetic wave, since the ion sheath is particularly strong on the inner wall member upper side 302, more ions in the plasma are incident. For this reason, it is considered that it is eroded remarkably, and physical sputtering and chemical etching occur around the inner wall member.

For this reason, the most reaction product is generated and deposited most on the outer portion of the shower plate near the vicinity where ions are incident most, and the deposition amount of the reaction product gradually decreases as the distance from the reaction plate increases. The electrode cover 236 is far from the reaction product generation source, but the reaction product is easily deposited because the surface of the electrode cover 236 is lower than the temperature of the inner wall member.

The inner wall member 216 is coated with a Y ₂ O ₃ sprayed film, but this sprayed film easily changes to YF ₃ in a fluorine atmosphere. For this reason, YF ₃ or CF-based reaction products are deposited on the lower surface of the inner wall member 216.

Y ₂ O ₃ and YF ₃ are non-volatile, and their melting points are 2410 ° C. and 1152 ° C., respectively. For this reason, once the reaction product adheres, it is difficult to remove the reaction product, and the deposited film gradually increases in thickness as wafer processing is repeated.

  Next, based on the analysis result of the reaction product and the degree of influence on the etching rate of each part to which the reaction product adheres, the influence of the reaction product attached to the inner wall of the vacuum vessel on the atmosphere in the vacuum vessel Think about the mechanism of change over time.

  In particular, a fluorine-based process that causes a change with time uses a deposition fluorine-containing gas containing carbon and an etching fluorine-containing gas containing sulfur in terms of the uniformity of the etching rate. For this reason, it is considered that the etching rate is increased by relatively increasing fluorine radicals and ions in the vacuum vessel.

  FIG. 8 is a diagram showing how the supplied process gas is consumed in the vacuum vessel, and FIG. 8A is a diagram showing the consumption ratio of the process gas immediately after cleaning the processing chamber. FIG. 8B is a diagram for explaining a first mechanism (mechanism of process gas consumption) that the reaction product affects the atmosphere, and FIG. 8C is a second mechanism that the reaction product affects the atmosphere. FIG. 8D is a diagram for explaining a third mechanism in which the reaction product affects the atmosphere.

In the state immediately after cleaning the processing chamber shown in FIG. 8A, 801 is the amount of process gas supplied, 802 is the amount of gas consumed by the wafer, 803 is the amount of gas consumed by the shower plate, and 804 is the electrode cover. 805 indicates the amount of gas consumed by the Y ₂ O ₃ member (sprayed film), and 806 indicates the amount of gas consumed by the other (exhaust etc.).

As shown in the figure, most of the gas reacts with Poly-Si on the wafer, but a part is considered to be consumed by the shower plate, the electrode cover, the Y ₂ O ₃ member, exhaust, and the like.

  Next, based on these matters, the mechanism when the reaction product is deposited will be described. In addition, it is thought that the mechanism in which the reaction product deposited by repeated wafer processing influences the atmosphere in the vacuum vessel is due to the following three points.

  First, the first mechanism is shown in FIG. Immediately after cleaning the processing chamber, the gas reacts with quartz members such as a shower plate and an electrode cover. However, when the reaction product generated by the repeated wafer processing covers the quartz member, the reaction between the quartz member and the gas decreases. For this reason, excess gas will stay in a vacuum vessel, and more gas will react with a wafer.

The second mechanism is shown in FIG. As the wafer processing is repeated, the reaction product 807 containing fluorine adheres to the shower plate, the electrode cover, the Y ₂ O ₃ member, and the like. In this case, the reaction product 807 containing fluorine releases fluorine by physical collision from plasma or chemical reaction. As a result, the fluorine atmosphere in the chamber becomes higher, and more fluorine reacts with the wafer.

  A third mechanism is shown in FIG. When the reaction product adheres to the inner wall of the vacuum vessel, the process gas is easily adsorbed by the reaction product. As the process gas, a deposition gas and an etching gas are used. In this case, since the deposition gas 808 is more easily adsorbed than the etching gas 809, the etching gas in the chamber is relatively increased, and as a result, more etching gas is absorbed in the wafer. Will react.

  Next, based on the above knowledge, a plasma processing apparatus including a shower plate, an electrode cover, and a processing chamber inner wall structure capable of suppressing changes with time was considered.

  9, 10, and 11 are views for explaining a plasma processing apparatus capable of suppressing such a change with time. FIG. 9 shows a film (spraying) containing Y on the surface of the processing chamber inner wall, the shower plate, and the electrode cover. FIG. 10 shows an example in which the walls of the processing chamber, the shower plate (excluding the central portion of the shower plate) and the electrode cover are coated with a film containing Y (a sprayed coating), and FIG. 11 shows the processing chamber. A film containing Y is positioned on the surface of the wall, shower plate (except the center of the shower plate) and electrode cover, and the center of the shower plate, facing the daylighting window of the optical fiber 303 for detecting plasma emission ( It is a figure which shows the example coat | covered with the transparent film.

  FIG. 9 basically shows a structure in which the entire surface of the processing chamber is covered with a plasma resistant material (a sprayed film containing Y). As described above, the reaction product adheres to the inner wall of the processing chamber by overlapping the wafer processing. However, since the inner wall of the processing chamber is coated with the plasma-resistant material and is equivalent to the state in which the reaction product is already coated, the influence of the newly deposited reaction product on the atmosphere in the vacuum vessel is small. . For this reason, it becomes possible to reduce a change with time.

  A thermal spraying method is widely used as a method for coating a material containing Y. However, a film (sprayed film) generated by thermal spraying is opaque, and it is difficult to use an end point determination device using light interference or the like. In such a case, it is desirable to form a film transparently using a CVD method, an AD (aerosol deposition) method, or the like.

  FIG. 10 shows an example in which a film containing Y is not formed at the center of the shower plate. As described above, the center portion of the shower plate is shaved by etching, so that the amount of the reaction product attached is small. For this reason, it is not necessary to coat the material containing Y, and the shower plate (quartz member) can be exposed only at the central portion as shown in FIG. In this case, the end point is determined through the shower plate and the quartz plate in the central portion.

  Note that any type of coating method may be used as long as it covers up to a position that does not affect the light receiving portion of the end point detection system above the shower plate. However, if there is an influence, it is desirable to form a transparent film on the portion by the CVD method or the AD method. It is also possible to cope by shifting the light receiving part of the detection system to a position where it is not affected.

  FIG. 11 shows an example in which a transparent plasma-resistant material is used on the surface corresponding to the light receiving portion of the end point detection system of the shower plate.

  As described above, when the shower plate is disposed so as to be exposed, the end point can be detected. However, the amount of light received decreases when the shower plate is scraped. For this reason, as shown in FIG. 11, it is preferable to coat only the surface corresponding to the light receiving portion with a transparent plasma-resistant material.

  When covered with an opaque substance, it is also possible to make a hole for daylighting to determine the end point. In this case, it is necessary to set the size so that abnormal discharge does not occur around the hole.

  It is also possible to divide the parts between the place where the reaction product of the shower plate adheres (outer peripheral side) and the part where the reaction product is scraped (inner peripheral side) to make a combination of two or more parts.

  When coating the surface of the electrode cover with a plasma-resistant film, a CVD method or an AD method can be used in addition to the thermal spraying. It can also be configured as a sintered body. In the case of a sintered body, it is difficult to regenerate, but the life of the part itself can be improved.

Note that the plasma-resistant film that covers the inner wall member 216, the inner chamber 221, the process gate valve 225, and the like is easily changed to YF ₃ in a fluorine atmosphere. For this reason, it is desirable to use YF ₃ as the plasma-resistant film.

  As described above, according to the present embodiment, the vacuum processing container constituting the plasma processing apparatus includes the cylindrical side wall member, the lid member that covers the upper portion of the side wall member, and the dielectric disposed on the side wall member side of the lid member. The outer peripheral portion of the inner wall surface of the side wall member and the side wall member side surface of the dielectric plate, that is, the region where the reaction product is deposited is covered with a plasma resistant material containing yttrium (Y).

  For this reason, even if the reaction product adheres to the inner wall of the processing chamber due to repeated wafer processing, a part of the wall surface of the processing chamber is covered with a plasma-resistant material equivalent to the adhering reaction product, and the reaction product has already been coated. Is equivalent to the state of being coated, so that the newly attached reaction product has little influence on the atmosphere in the vacuum vessel. Further, by covering the surface corresponding to the light receiving portion of the end point detection system with a transparent plasma resistant material, it is possible to suppress a decrease in the amount of received light due to a quartz plate such as a shower plate being shaved. In addition, it is possible to provide a plasma processing apparatus that can cause stable microfabrication over a long period of time with little damage to the wall surface of the processing chamber.

1 is a schematic plan view illustrating an overall configuration of a vacuum processing apparatus used in an embodiment of the present invention. It is a longitudinal cross-sectional view explaining the structure of the etching process unit shown in FIG. FIG. 3 is an enlarged view of the vicinity of a processing chamber of the etching processing unit (plasma processing apparatus) shown in FIG. 2. It is a figure explaining the temporal change of processing conditions. It is a figure explaining the adhesion situation of a reaction product. It is a figure which shows the component-analysis result of a reaction product. It is a figure explaining the mechanism in which a reaction product adheres. It is a figure which shows how the supplied process gas is consumed within a vacuum vessel. It is a figure explaining the plasma processing apparatus which can suppress a time-dependent change. It is a figure explaining the plasma processing apparatus which can suppress a time-dependent change. It is a figure explaining the plasma processing apparatus which can suppress a time-dependent change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Vacuum processing apparatus 101 Atmosphere side block 102 Processing block 103,104 Processing unit 105,106 Transfer unit 107 Control unit 108 Case 109 Wafer cassette 110 Dummy cassette 111 Positioning part 113 Lock chamber 200 Processing unit 201 Cover member 202 Antenna 203 Magnetic field Generator (coil)
205 High-frequency power source 206 Dielectric 207 Quartz plate 208 Shower plate 209 Sample stage 210 Discharge chamber 211 Buffer chamber 212 Process gas line 213 Process gas shut-off valve 214 Controller (MFC)
215 Lower ring 216 Inner wall member 217 Outer wall member 218 Base plate 219, 220 Outer chamber 221, 222 Inner chamber 223 Vacuum chamber 224 Atmospheric gate valve 225 Process gate valve 226, 227 Driving means 228 Support beam 229 Support base member 230 Hanging beam 231 Exhaust valve 232 Exhaust pump 233 Exhaust gate plate 234 Electrostatic adsorption electrode 235 Dielectric film 236 Electrode cover 237 High voltage power supply 238 Bias power supply 239 Matching circuit 301 Magnetic field line 302 Upper side of inner wall member 303 Optical fiber (light receiving part)
501 Shower plate outer peripheral part 502 Shower plate middle part 503 Shower plate center part 504 Electrode cover upper surface 901 Plasma resistant material P Plasma
W wafer

Claims (6)

A vacuum processing container, a sample stage arranged in the vacuum processing container, a gas introducing means for introducing a process gas into the vacuum processing container, a magnetic field generating means for generating a magnetic field in the processing container, and a lower part of the vacuum processing container And an evacuation means for evacuating the gas in the container, supplying high-frequency power into the vacuum processing container to generate plasma by interaction with the magnetic field, and placing the plasma on the sample stage by the generated plasma In a plasma processing apparatus for performing plasma processing on a sample,
The vacuum processing container includes a cylindrical side wall member, a lid member that covers an upper portion of the side wall member, and a dielectric plate disposed on the side wall member side of the lid member,
A plasma processing apparatus, wherein a coating film containing yttrium (Y) is formed on an inner surface of the side wall member and an outer peripheral portion of a surface of the dielectric plate on the side wall member side. A vacuum processing container, a sample stage disposed in the vacuum processing container, a dielectric shower plate that disperses and introduces a process gas into the vacuum processing container, a magnetic field generating means for generating a magnetic field in the processing container, and An exhaust means is provided in the lower part of the vacuum processing container and exhausts the gas in the container. The high-frequency power is supplied into the vacuum processing container to generate plasma by interaction with the magnetic field. In the plasma processing apparatus for performing plasma processing on the sample placed on the sample stage,
The vacuum processing container includes a cylindrical side wall member, a lid member covering an upper portion of the side wall member, and the shower plate disposed on the side wall member side of the lid member,
A plasma processing apparatus, wherein a coating film containing yttrium (Y) is formed on an outer peripheral portion of an inner surface of the side wall member and a surface of the shower plate on the side wall member side. The plasma processing apparatus according to claim 1 or 2,
A plasma processing apparatus comprising a region where the coating film is not formed on an inner peripheral side of the side wall member side surface of the shower plate, and a photodetector arranged so as to detect plasma emission through the region. . The plasma processing apparatus according to claim 1 or 2,
A plasma processing apparatus, wherein a film containing yttrium (Y) is formed transparently by a CVD method or an AD method. The plasma processing apparatus according to claim 1 or 2,
An electrode cover is provided on the outer periphery of the sample stage, and a film containing yttrium (Y) is formed on the surface of the electrode cover. The plasma processing apparatus according to claim 1 or 2,
The plasma processing apparatus, wherein the film containing yttrium (Y) is Y ₂ O ₃ or YF ₃ .

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