JP5065725B2 - Plasma processing equipment - Google Patents

Description

  The present invention relates to a plasma processing apparatus that performs etching processing or film forming processing of a semiconductor substrate or a glass substrate using plasma, and more specifically, plasma is obtained by combining an annular magnetic neutral line having a zero magnetic field and an alternating electric field. The present invention relates to a plasma etching apparatus which generates

  In recent years, plasma etching apparatuses that perform etching of a substrate using plasma have been widely known. This type of plasma etching apparatus is classified into several methods depending on the configuration of the plasma source that generates the plasma. Among them, the plasma is generated by the combination of the electric field and the magnetic field formed in the vacuum chamber. A plasma etching apparatus is known. For example, Patent Document 1 discloses a plasma etching apparatus 10 shown in FIG.

  In FIG. 6, reference numeral 11 denotes a vacuum chamber, in which a reaction chamber 11a is formed. A vacuum pump 17 is connected to the vacuum chamber 11, and the inside of the vacuum chamber 11 is evacuated to a predetermined degree of vacuum. The cylindrical container 12 constituting the periphery of the reaction chamber 11a is made of a transparent material such as quartz, and on the outer peripheral side thereof is a high-frequency coil 13 for plasma generation connected to a high-frequency power source RF1, and the outer peripheral side of the high-frequency coil 13 The magnetic coil groups 14 including three magnetic coils 14A, 14B, and 14C are respectively disposed.

  A current in the same direction is supplied to the magnetic coil 14A and the magnetic coil 14C, and a current is supplied to the magnetic coil 14B in the opposite direction to the other magnetic coils 14A and 14C. As a result, in the reaction chamber 11a, an annular magnetic neutral line 15 having no magnetic field is formed, and an induction electric field is applied along the magnetic neutral line 15 by the high-frequency coil 13, thereby forming discharge plasma.

  A stage 16 that supports the substrate is installed inside the vacuum chamber 11. This stage 16 is connected to a bias power supply RF4. A top plate 18 that closes the upper portion of the cylindrical container 12 as an opposing electrode of the stage 16 is connected to a ground potential. The top plate 18 is provided with a gas introduction head 19 for introducing an etching gas into the reaction chamber 11a.

In the plasma etching apparatus 10 configured as described above, the formation position and the formation diameter of the magnetic neutral wire 15 can be adjusted by the magnitude of the current supplied to the magnetic coil group 14. Specifically, when the currents supplied to the magnetic coils 14A, 14B, and 14C are I _A , I _B , and I _C , respectively, when I _A > I _C , the formation position of the magnetic neutral wire 15 is on the magnetic coil 14C side. Conversely, when I _A <I _C , the formation position of the magnetic neutral line 15 rises toward the magnetic coil 14A. Also, when gradually increasing the current I _B supplied to the intermediate magnetic coil 14B, at the same time when the ring diameter of the magnetic neutral line 15 becomes small, it becomes gentle gradient of the magnetic field at the position of the zero magnetic field. Therefore, it is possible to optimize the plasma density distribution by using these characteristics.

JP 7-263192 A

  However, in the plasma etching apparatus 10 having the above-described configuration, the position of the magnetic neutral line 15 can be controlled only when the pressure in the reaction chamber 11a is relatively low (for example, 1.5 Pa or less). That is, there is a problem that it becomes more difficult to adjust the plasma distribution by current control on the magnetic coil group 14 as the pressure in the reaction chamber 11a becomes higher.

  In general, in plasma etching, a higher etching rate is obtained as the amount of introduced etching gas increases. Actually, the etching process is performed under a pressure of about 2 to 10 Pa, for example. Therefore, in the plasma etching apparatus using the magnetic neutral line, it is impossible to adjust the plasma distribution when the pressure in the reaction chamber is relatively high. Therefore, the etching rate is directly below the magnetic neutral line 15. In-plane non-uniformity such as a high etching distance is low at a position away from the magnetic neutral line 15 becomes apparent. In particular, in the plasma processing step of forming holes or grooves having a high aspect ratio on the surface of the Si substrate by alternately performing the etching process and the formation of the sidewall protective film, the in-plane variation in the etching rate is increased. It is not possible to obtain an etching distribution.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a plasma processing apparatus capable of adjusting the plasma distribution even when the pressure in the reaction chamber is relatively high.

  In solving the above problems, the plasma processing apparatus of the present invention includes a vacuum chamber that forms a reaction chamber, a top plate that closes the upper portion of the vacuum chamber, and a first high-frequency power source disposed around the reaction chamber. A first plasma source connected to the substrate, a substrate support stage installed in the reaction chamber and connected to a predetermined bias power source, a gas introduction means for introducing a process gas into the reaction chamber, and a reaction chamber A plasma processing apparatus comprising a magnetic field forming means for forming an annular magnetic neutral line having a zero magnetic field, wherein the top plate has a second plasma source for plasma distribution adjustment connected to a second high-frequency power source. Is installed.

  In the plasma processing apparatus of the present invention, the formation density of the electric field is increased on the radially inner side of the magnetic neutral wire by installing the second plasma source on the top plate that closes the upper part of the vacuum chamber. . As a result, even when the pressure in the reaction chamber is relatively high, the plasma distribution can be adjusted by the second plasma source, and the in-plane plasma processing on the substrate can be made uniform.

  In the present invention, the top plate has an opening at the center, and the second plasma source is installed through the dielectric with respect to the opening. In this way, by installing the second plasma source only in a predetermined region of the top plate, the electric field region formed by the second plasma source can be limited to a desired radially inward region of the magnetic neutral line. The plasma density in the region can be increased.

  The second plasma source is an RF (Radio Frequency) antenna configured by connecting an antenna to the second high-frequency power source, or an RF electrode comprising an electrode connected to the second high-frequency power source via a capacitor Can be configured. When the second plasma source is constituted by an RF antenna, a window member made of a transparent material such as quartz is preferably used as the dielectric.

  Further, by connecting a high frequency power source to the top plate, it is possible to suppress the generation of dust due to film adhesion to the top plate, compared to a configuration in which the top plate is connected to the ground potential. In addition, by installing a sputtering target on the top plate, it is possible to configure a plasma processing apparatus that performs a film forming process in addition to an etching process. In this case, the high frequency power source connected to the top plate may be a second high frequency power source connected to the second plasma source, or may be a third high frequency power source different from the second high frequency power source. In the former case, it is preferable to provide a switching means for selectively switching the connection of the top plate and the second plasma source to the second high-frequency power source.

  According to the plasma processing apparatus of the present invention, since the second plasma source for plasma adjustment is installed on the top plate that closes the upper part of the vacuum chamber, the plasma can be obtained even when the pressure in the reaction chamber is relatively high. The distribution can be adjusted, and in-plane uniformity of the plasma processing on the substrate can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a side sectional view showing a schematic configuration of a plasma processing apparatus 20 according to an embodiment of the present invention. In the present embodiment, an example will be described in which the present invention is applied to a plasma processing apparatus that forms holes or grooves with a high aspect ratio on the surface of a Si substrate by alternately performing an etching process and forming a sidewall protective film.

  In FIG. 1, reference numeral 21 denotes a vacuum chamber, in which a reaction chamber 21a is formed. A vacuum pump 27 such as a turbo molecular pump is connected to the vacuum chamber 21, and the inside of the vacuum chamber 21 is evacuated to a predetermined degree of vacuum.

  The cylindrical container 22 constituting the periphery of the reaction chamber 21a is made of a transparent material such as quartz, and on the outer peripheral side thereof, a high frequency coil 23 for plasma generation connected to a first high frequency power source RF1 and the high frequency coil 23 are provided. A magnetic coil group 24 composed of three magnetic coils 24A, 24B, and 24C is disposed on the outer peripheral side of each. Here, the high frequency coil 23 corresponds to the “first plasma source” of the present invention, and the magnetic coil group 24 corresponds to the “magnetic field forming means” of the present invention.

  A current in the same direction is supplied to the magnetic coil 24A and the magnetic coil 24C, and a current is supplied to the magnetic coil 24B in the opposite direction to the other magnetic coils 24A and 24C. As a result, an annular magnetic neutral line 25 having a zero magnetic field is formed in the reaction chamber 21a, and an induction electric field is applied along the magnetic neutral line 25 by the high-frequency coil 23, whereby discharge plasma is generated in the reaction chamber 21a. It is formed.

  A stage 26 for supporting the substrate 30 is installed in the reaction chamber 21a. The stage 26 is made of metal, and is connected to a fourth high-frequency power source RF4 as a bias power source via a capacitor 31. By connecting the fourth high-frequency power source RF4 to the stage 26, ions can be accelerated to the stage 26 side by the substrate bias, and radical products on the substrate 30 can be removed by sputtering to improve the etching performance.

  A gas introduction nozzle 29 for introducing a process gas into the reaction chamber 21a is installed on the upper portion of the cylindrical container 22. As the process gas, a rare gas such as Ar or He and an etching gas are used. The etching gas is appropriately selected depending on the object to be etched. For example, when etching a Si-based material, a halogen-based gas such as SF-based, CF-based, CHF-based, or a mixed gas of this and a rare gas is used. .

  The upper part of the cylindrical container 22 is closed with a top plate 28. The top plate 28 is made of metal and is configured as a counter electrode of the stage 26. The top plate 28 is connected to a third high-frequency power source RF3 as a bias power source via a capacitor 32. The high frequency power supply RF3 suppresses charge-up due to positive ions in the etching region, and realizes etching processing with a high aspect ratio.

  The top plate 28 has an opening 28a at the center. A window member 33 made of a dielectric is installed in the opening 28a. The window member 33 is made of a transparent material such as quartz or translucent ceramics. The window member 33 is provided with a loop-shaped RF antenna 34 for plasma generation connected to the second high-frequency power source RF2. The RF antenna 34 constitutes a second plasma source for adjusting the density distribution of the plasma generated in the reaction chamber 21a.

  In the present embodiment, the loop diameter of the RF antenna 34 is set to be smaller than the diameter of the annular magnetic neutral wire 25 formed by the magnetic coil group 24, and the loop center of the RF antenna 34 is magnetic. The window member 33 is installed so as to substantially coincide with the center of the sex line 25. The loop diameter of the RF antenna 34 is selected as appropriate, and is set to such a size that a desired plasma distribution can be obtained in the radially inward region of the magnetic neutral wire 25.

  Above the window member 33, a sensor 41 for detecting the surface to be processed of the substrate 30 on the stage 26 is installed. The sensor 41 is composed of a solid-state imaging device such as a CCD and an optical detector such as a photocoupler. By using the window member 33 as the detection window of the sensor 41, the etching depth of the substrate 30 can be detected in real time, unlike when the substrate is monitored from the lateral direction. For example, when it is desired to remove the entire resist film on the substrate surface, it is possible to confirm in real time how the resist film is removed in the surface.

  A sputtering target 35 is installed on the surface of the top plate 28 facing the reaction chamber 21a. The target 35 is sputtered by ions in the plasma formed in the reaction chamber 21a, and the sputtered material is deposited on the surface of the substrate 30 on the stage 26. In the present embodiment, a synthetic resin material such as polytetrafluoroethylene (PTFE) is used as a constituent material of the target 35. Note that the constituent material of the target 35 is not limited to a synthetic resin material, and a single material such as metal, silicon, ceramics, or a composite material thereof can be used.

  In the plasma processing apparatus 20 of this embodiment configured as described above, the surface of the substrate 30 on the stage 26 is etched by generating plasma of an etching gas in the reaction chamber 21a. A resist pattern having a predetermined shape is formed on the surface of the substrate 30 in advance, and etching proceeds in the opening of the resist pattern. On the other hand, by generating rare gas plasma in the reaction chamber 21a, the target 35 installed on the top plate 28 is sputtered, and the sputtered material is attached to the surface of the substrate 30 and the bottom and side walls of the etching pattern. By alternately performing the etching process and the sputtering process, holes or grooves having a high aspect ratio can be formed on the surface of the substrate 30 with high accuracy.

FIG. 2 is a timing chart showing the relationship between the introduction timing of the etching gas and the rare gas and the application timing of the high frequency power sources RF1 to RF4. In this example, SF ₆ gas is used as the etching gas, and Ar gas is used as the rare gas.

  RF1 and RF4 are always applied to the high-frequency antenna 23 and the stage 26. When supplying power to the high-frequency antenna 23, predetermined power is also supplied to the magnetic coil group 24. Therefore, high-density plasma is formed in the reaction chamber 26a along the magnetic neutral line 25, and ions in the plasma are periodically drawn to the stage 26 side.

During the etching process of the substrate 30 (time t1 to t2), an etching gas (SF ₆ ) is introduced into the reaction chamber 21a, and plasma of the etching gas is formed. The pressure in the reaction chamber 21a at this time is set to 2 Pa to 10 Pa, for example. Under such a relatively high-pressure reduced pressure atmosphere, it is impossible to adjust the plasma distribution even if current supply control is performed on the magnetic coil group 24. Therefore, by applying the high frequency power supply RF2 to the RF antenna 34 as the second plasma source, the plasma distribution is adjusted so that the plasma density at the radially inner position of the magnetic neutral wire 25 is increased. Thereby, the uniformity of the etching rate within the surface of the substrate 30 is improved.

  According to the present embodiment, since the RF antenna 34 as the second plasma source is installed only in a predetermined region of the top plate 28, the electric field region formed by the second plasma source is magnetically It can be limited to a desired inner diameter region of the property line 25, and the plasma density in the region can be increased.

  Further, since the RF antenna 34 is installed on the window member 33, film adhesion to the window member 33 can be suppressed, thereby maintaining the translucency of the window member 33 stably, and an etching process using the sensor 41. It is possible to perform continuous monitoring.

  On the other hand, at the time of forming the sidewall protective film (time t2 to t3), the introduction of the etching gas is stopped, and plasma of only a rare gas is formed. In addition, the high frequency power supply RF2 is turned off to the RF antenna 34, and the bias power supply RF3 is applied to the top board 28 instead. By applying the bias power supply RF3, a sputtering action of ions in plasma with respect to the top plate 28 is obtained. As a result, the reaction product of the etching gas adhering to the top plate 28 is removed, and at the same time, the target 35 is sputtered and the sputtered material adheres to the bottom and side walls of the etching pattern of the substrate 30 to form a protective film. .

In the side wall protective film forming step, the pressure in the reaction chamber 21a is set to 0.1 Pa to 1.5 Pa, for example. Under such a relatively low-pressure reduced-pressure atmosphere, it is possible to adjust the formation region of the magnetic neutral line 25, that is, the plasma distribution, only by controlling the current to the magnetic coil group 24. Specifically, when the currents supplied to the magnetic coils 24A, 24B, and 24C are I _A , I _B , and I _C , respectively, when I _A > I _C , the formation position of the magnetic neutral wire 25 is the magnetic coil 24C. Conversely, when I _A <I _C , the formation position of the magnetic neutral line 25 rises to the magnetic coil 14A side. Also, when gradually increasing the current I _B supplied to the intermediate magnetic coil 24B, at the same time when the ring diameter of the magnetic neutral line 25 becomes small, it becomes gentle gradient of the magnetic field at the position of the zero magnetic field. Therefore, by utilizing these characteristics, it is possible to optimize the plasma density distribution, and the uniformity of the deposition rate of the protective film on the surface of the substrate 30 can be improved.

  After the protective film is formed for a predetermined time, the etching gas is again introduced into the reaction chamber 21a, and the same etching process as described above is performed again. At this time, in the initial stage of etching, the protective film formed on the surface of the substrate 30 and the bottom of the etching pattern is removed by the sputtering action of ions in the plasma. Since the ions are incident substantially perpendicular to the substrate, the protective film attached to the side wall portion of the etching pattern remains without being completely removed.

  As described above, deep digging with a high aspect ratio is performed on the surface of the substrate 30. According to the present embodiment, during the etching process, the plasma distribution is adjusted using the second plasma source so as to improve the in-plane uniformity of the etching rate, and when the protective film is formed, the magnetic coil group 24 is used. Since the in-plane uniformity of the film formation rate is improved by adjusting the plasma distribution by controlling the current with respect to the above, it is possible to realize a highly accurate deep digging in the plane of the substrate 30.

FIG. 3 shows one experimental result showing in-plane (XY direction) uniformity of the etching rate depending on whether or not the second plasma source (RF antenna 34) is installed. The experimental conditions are as follows.
[Experimental conditions]
・ RF1: 13.56MHz, 3kW
・ RF2: 12.5MHz, 0.5kW
・ RF3: 12.5MHz, 0.5kW
Etching gas: SF ₆ + Ar
・ Etching pressure: 10Pa
・ Board size: 8 inches

  As is apparent from the results of FIG. 3, when there is no second plasma source, the etching rate is high on the outer peripheral side of the substrate. This indicates that a plasma distribution corresponding to the formation position of the magnetic neutral line is generated. On the other hand, it can be seen that the in-plane uniformity of the etching rate is improved by installing the second plasma source. This is because the formation density of the electric field is increased on the radially inner side (substrate central side) of the magnetic neutral wire by the installation of the second plasma source, and as a result, the etching rate of the outer peripheral portion of the substrate is reduced, and the substrate This is because the etching rate at the center is increased.

  FIG. 4 is a schematic configuration diagram of a main part of a plasma processing apparatus according to another embodiment of the present invention. The illustrated plasma processing apparatus has a configuration in which the high frequency power source RF2 of the RF antenna (second plasma source) 34 is also used as the bias power source of the top plate 28. In this case, a switch 36 serving as a switching unit is connected between the high frequency power source RF2, the top panel 28 (capacitor 32), and the RF antenna 34. The switch 36 has a function of selectively switching the connection of the top panel 28 and the RF antenna 34 to the high frequency power supply RF2.

  With the above configuration, it is possible to selectively switch between the power input to the RF antenna 34 and the power input to the top plate 28 by the switching operation by the switch 36. Therefore, in the plasma processing apparatus that alternately performs the etching process and the film forming process. The power can be easily and accurately switched. In addition, it is possible to reduce the power installation cost and simplify the control circuit.

  FIG. 5 is a schematic configuration diagram of a main part of a plasma processing apparatus according to still another embodiment of the present invention. The illustrated plasma processing apparatus shows an example in which the second plasma source is configured by an RF electrode 37 instead of an RF antenna. The RF electrode 37 is made of metal, is disposed in the opening 28a of the top plate 28 via a dielectric 38, and is connected to the high frequency power source RF2 via a capacitor 39 and a switch 36. The high frequency power supply RF2 is not limited to being shared by the RF electrode 37 and the top plate 28, and may be configured by a dedicated high frequency power supply for the RF electrode 37.

  As shown in FIG. 1, the plasma processing apparatus according to the present embodiment replaces an example in which an inductively coupled (ICP) type plasma source with an RF antenna 34 is used, and a capacitively coupled (CCP) type using a stage 26 as a counter electrode. This constitutes the plasma source. This example also makes it possible to adjust the density distribution of the plasma formed in the reaction chamber 21a, and to improve the in-plane uniformity of the etching rate.

  As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to this, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in the above embodiment, the plasma processing apparatus that forms the high aspect ratio hole or groove by alternately performing the etching process and the film forming process on the substrate has been described as an example. The present invention can also be applied to a plasma etching apparatus specialized for the above.

It is a sectional side view which shows schematic structure of the plasma processing apparatus by embodiment of this invention. It is a timing chart which shows an example of operation | movement of the plasma processing apparatus of FIG. It is an example of in-plane distribution of the etching rate explaining the effect | action of the plasma processing apparatus of FIG. It is a schematic block diagram of the principal part of the plasma processing apparatus by other embodiment of this invention. It is a schematic block diagram of the principal part of the plasma processing apparatus by further another embodiment of this invention. It is a sectional side view which shows schematic structure of the conventional plasma etching apparatus.

Explanation of symbols

20 Plasma processing equipment 21 Vacuum chamber 23 High frequency coil (first plasma source)
24 Magnetic coil group (magnetic field forming means)
25 Magnetic neutral wire 26 Stage 27 Vacuum pump 28 Top plate 29 Gas introduction nozzle (gas introduction means)
30 Substrate 33 Window member (dielectric)
34 RF antenna (second plasma source)
35 target 36 switch (switching means)
37 RF electrode (second plasma source)
38 Dielectric 41 Sensor RF1 First High Frequency Power Supply RF2 Second High Frequency Power Supply RF3, RF4 Bias Power Supply

Claims (7)

A vacuum chamber forming a reaction chamber;
A top plate that has an opening in the center, and a dielectric is installed in the opening, closing the upper part of the vacuum chamber;
A first plasma source disposed around the reaction chamber and connected to a first high frequency power source;
A stage for supporting a substrate installed in the reaction chamber and connected to a predetermined bias power source;
Gas introduction means for introducing process gas into the reaction chamber;
A magnetic field forming means for forming an annular magnetic neutral line having no magnetic field in the reaction chamber ;
A second plasma that is installed in the opening via the dielectric and is connected to a second high-frequency power source and capable of adjusting the plasma distribution so that the plasma density at the radially inner position of the magnetic neutral wire is increased. The source ,
A plasma processing apparatus comprising: The plasma processing apparatus according to claim 1 , wherein the dielectric is made of a transparent material, and the second plasma source is an RF antenna. The plasma processing apparatus of Claim 2. The sensor which optically monitors the to-be-processed surface of the board | substrate inside a vacuum chamber through the said dielectric material. The plasma processing apparatus according to claim 1, wherein the second plasma source is an RF electrode. The plasma processing apparatus according to claim 1, wherein the top plate is connected to a third high-frequency power source different from the second high-frequency power source. The top plate and the second plasma source are connected to the second high-frequency power source via a switching unit, and the switching unit includes the top plate and the second plasma for the second high-frequency power source. The plasma processing apparatus according to claim 1, wherein the source connection is selectively switched. The plasma processing apparatus according to claim 1, wherein a sputtering target is installed on a surface of the top plate that faces the reaction chamber.

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