JP5174848B2 - Plasma processing method and plasma processing apparatus - Google Patents

Description

  The present invention relates to a technique for performing plasma processing on a substrate to be processed, and more particularly to a single-wafer type plasma processing method and apparatus for generating plasma using high-frequency discharge.

  In processes such as etching, deposition, oxidation, sputtering and the like in the manufacturing process of semiconductor devices and FPDs (Flat Panel Displays), plasma is often used in order to allow a process gas to react well at a relatively low temperature. In general, methods for generating plasma in a plasma processing apparatus are roughly classified into those using glow discharge or high-frequency discharge and those using microwaves.

  In general, in a single wafer plasma processing apparatus using high frequency discharge, a mounting table or a susceptor that also serves as an electrode is installed in a chamber that can be decompressed, and a substrate to be processed (semiconductor wafer, glass substrate, etc.) is placed on the susceptor. ) Is placed. Then, after reducing the pressure in the chamber to a predetermined degree of vacuum, a processing gas is introduced, and a high frequency is applied to the electrode when the gas pressure in the chamber reaches a set value. Then, the process gas starts to discharge and gas plasma is generated. Under this plasma, the surface of the substrate or the surface to be processed is subjected to film microfabrication (such as dry etching) or film formation (such as chemical vapor deposition).

  In a high-frequency discharge type plasma processing apparatus, when the gas pressure is low, the density of gas molecules is low, so that it is difficult to start or maintain the discharge (plasma ignition). In particular, in the parallel plate type plasma processing apparatus, not only the tendency is remarkable, but even if the electrode interval is narrowed or the RF voltage applied between the electrodes is lowered, the energy obtained from the electric field by the electric field and the gas There is a tendency for the discharge to become unstable due to less energy for ionizing molecules or atoms. However, some plasma processing may have low gas pressure, sandwiched electrode spacing, or low RF applied voltage as desirable processing conditions. For example, in anisotropic etching, a low gas pressure is advantageous for obtaining a good vertical etching shape, and stable discharge start characteristics and discharge maintenance characteristics in a low pressure region are required.

  Conventionally, discharge is started under special high-pressure conditions suitable for discharge (see, for example, Patent Document 1), or discharge is started under different gas conditions or high RF application conditions. A method (ignition plasma method) for switching to the above processing conditions is known. It is also known that a method of assisting plasma generation with microwaves or UV light is also effective.

JP 2003-124198 A

  However, since the ignition plasma method uses conditions different from the original processing conditions for a certain period of time, there are disadvantages that affect the process and reduce the throughput. In addition, the method using microwaves or UV light is not only concerned with the influence on the process, but also has the disadvantage that the apparatus becomes complicated and the apparatus cost increases. After all, conventionally, microwave applications such as ECR (Electron Cyclotron Resonance) have been used for low-pressure plasma applications.

  The present invention has been made in view of the above-described problems of the prior art, and provides a plasma processing method and a plasma processing apparatus that can easily start a high-frequency discharge at a low cost and maintain a stable discharge. .

  The present invention also provides a plasma processing method and a plasma processing apparatus that effectively confine plasma on a substrate to be processed at a high density to improve the reaction rate and in-plane uniformity of plasma processing.

  In the plasma processing method of the present invention, a processing gas is flowed into a depressurizable chamber, a high-frequency electric field is formed to generate plasma of the processing gas, and a plasma for performing a desired plasma processing on a substrate to be processed under the plasma. In the processing method, the magnetic lines of force pass only in the peripheral plasma region radially outside the outer peripheral edge of the substrate in the plasma generation space in the chamber, and both the starting point and the ending point of the magnetic line of force are passed through this region. Forms a magnetic field located radially inward of the side wall of the chamber, and in the magnetic field, both the starting point and the ending point of the magnetic field lines are located above the peripheral plasma region, and the magnetic field lines exiting from the starting point are A U-turn is made in or below the peripheral plasma region to reach the end point, and a first point and an end point of the magnetic field lines are respectively provided. And the second magnetic pole is a magnet, and between the first and second magnetic poles, the magnetic quantity arranged on the radially outer side is larger than the magnetic quantity arranged on the radially inner side. Largely, the main plasma region radially inward from the outer peripheral edge of the substrate in the plasma generation space is substantially in the absence of a magnetic field.

  The plasma processing apparatus of the present invention also includes a chamber capable of decompression, an electrode for placing a substrate to be processed in the chamber substantially horizontally, and a processing gas in a plasma generation space set above and around the electrode. A processing gas supply unit to supply, a high-frequency electric field forming mechanism for forming a high-frequency electric field in the plasma generation space, and only a peripheral plasma region radially outside the outer peripheral edge of the substrate in the plasma generation space in the chamber, A magnetic field forming mechanism that forms a magnetic field in which magnetic field lines pass through the region and both the starting point and the ending point of the magnetic field lines are located radially inward of the side wall of the chamber, the magnetic field forming mechanism , Both the first and second magnetic poles are disposed downward and above the peripheral plasma region, and the magnetic field exits the first magnetic pole at the starting point in the magnetic field. The field lines fall into the peripheral plasma region and then make a U-turn to reach the second magnetic pole at the end point, and both the first and second magnetic poles respectively giving the start point and end point of the magnetic field lines are magnets, Between the first and second magnetic poles, the amount of magnetism arranged on the radially outer side is larger than the amount of magnetism arranged on the radially inner side, and the outer peripheral edge of the substrate in the plasma generation space In the main plasma region on the radially inner side, a substantially no magnetic field is set.

  In the present invention, in a plasma processing apparatus that generates plasma of a processing gas by high-frequency discharge in a depressurizable chamber, the magnetic field forming mechanism is only in a peripheral plasma region radially outside the outer peripheral edge of the substrate in the plasma generation space. Create a substantial magnetic field. As a result, during plasma processing, if the high-frequency electric field formation mechanism forms a high-frequency electric field in the plasma generation space, the process gas starts to discharge first in the surrounding plasma region where the magnetic field exists, and plasma is generated instantaneously from there. Discharge expands throughout the space and discharge or plasma generation is established. Thereafter, since the magnetic field assists the high frequency discharge in the peripheral plasma region, as long as the supply of the processing gas and the application of the high frequency are maintained, the discharge or plasma generation is stably maintained in the entire plasma generation space. As described above, the magnetic field in the peripheral plasma region serves as a trigger for the start of the high frequency discharge and assists the discharge maintenance, so that the discharge can be easily started and maintained stably even under a low gas pressure condition, for example. On the other hand, since the magnetic field forming mechanism can make the main plasma region substantially non-magnetic, it can avoid or reduce the possibility that the magnetic field acts on the substrate on the electrode to cause damage or stress.

  Further, in the present invention, the magnetic lines of force pass through only the peripheral plasma region radially outside the outer peripheral edge of the substrate in the plasma generation space in the chamber, and both the start point and the end point of the magnetic force line are in the chamber. A magnetic field is formed so as to be located radially inward of the side wall. Here, in the magnetic field forming mechanism, both the first and second magnetic poles are disposed downward and above the peripheral plasma region, and in the magnetic field, the lines of magnetic force emitted from the first magnetic pole at the start point are the peripheral plasma region. Go down and make a U-turn at a lower height than the substrate to reach the second magnetic pole at the end point. According to such a magnetic pole arrangement structure, compared with a configuration in which the magnetic field forming mechanism is arranged outside the side wall of the processing vessel, the radial distance and the circulation distance with respect to the chamber center are remarkably short, so that it is suitable for the peripheral plasma region. The number of magnets or magnetic poles and the amount of magnetic force for forming a magnetic field of a profile (that is, a profile in which a strong magnetic field is obtained as close to the main plasma region as possible without magnetically affecting the main plasma region) ( (Proportional to size or volume) can be greatly reduced, and the increase in device size and cost associated with the provision of the magnetic field forming mechanism can be minimized.

  In addition, the present invention provides a magnetic field line loop for U-turning the magnetic field lines in the peripheral plasma region by disposing the first and second magnetic poles that respectively provide the starting point and the end point of the magnetic field lines as described above, both downward and above the peripheral plasma region. With the structure, the magnetic flux density in the peripheral plasma region can be increased, and at the same time, the flow of magnetic lines of force to the main plasma region can be effectively prevented. In addition, between the first and second magnetic poles, the magnetic amount arranged on the radially outer side is larger than the magnetic amount arranged on the radially inner side, so that the effect of the magnetic field line loop structure is further enhanced. Can be increased.

  According to the plasma processing method or the plasma processing apparatus of the present invention, it is possible to easily start the high frequency discharge at a low cost and to maintain the discharge stably by the above configuration and operation. Furthermore, the plasma on the substrate to be processed can be effectively confined to improve the plasma processing reaction speed and in-plane uniformity.

It is sectional drawing which shows the structure of the plasma etching apparatus in one Embodiment of this invention. It is a perspective view which shows the structure of the principal part of the magnetic field formation mechanism in embodiment. It is sectional drawing which shows the structure of the principal part of the magnetic field formation mechanism in embodiment. It is a graph which shows magnetic field strength distribution in the plasma production space in one Example. It is a graph which shows magnetic field strength distribution in the plasma production space in one Example. It is a schematic sectional drawing which shows typically an effect | action of the magnetic field formation mechanism in embodiment. It is sectional drawing which shows the structure of the modification of the magnetic field formation mechanism in embodiment. It is a top view which shows the principal part of the modification of FIG. It is sectional drawing which shows the structure of the principal part of the magnetic field formation mechanism by one Example. It is sectional drawing which shows the structure of the principal part of the magnetic field formation mechanism by one Example. It is sectional drawing which shows the structure of the principal part of the magnetic field formation mechanism by one modification. It is sectional drawing which shows the structure of the principal part of the magnetic field formation mechanism by one modification.

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

  FIG. 1 shows the configuration of a plasma processing apparatus according to an embodiment of the present invention. This plasma processing apparatus is configured as a parallel plate type plasma etching apparatus, and has a cylindrical chamber (processing vessel) 10 made of metal such as aluminum or stainless steel. The chamber 10 is grounded for safety.

  In the chamber 10, for example, a disk-like lower electrode or susceptor 12 on which a semiconductor wafer W is placed is provided as a substrate to be processed. The susceptor 12 is made of, for example, aluminum, and is supported by a cylindrical support portion 16 that extends vertically upward from the bottom of the chamber 10 via an insulating cylindrical holding portion 14. On the upper surface of the cylindrical holding part 14, a focus ring 18 made of quartz, for example, surrounding the upper surface of the susceptor 12 in an annular shape is disposed.

  An exhaust passage 20 is formed between the side wall of the chamber 10 and the cylindrical support portion 16, and an annular baffle plate 22 is attached to the entrance or midway of the exhaust passage 20 and an exhaust port 24 is provided at the bottom. . An exhaust device 28 is connected to the exhaust port 24 via an exhaust pipe 26. The exhaust device 28 includes a vacuum pump, and can reduce the processing space in the chamber 10 to a predetermined degree of vacuum. A gate valve 30 that opens and closes the loading / unloading port of the semiconductor wafer W is attached to the side wall of the chamber 10.

  A high frequency power supply 32 for generating plasma is electrically connected to the susceptor 12 via a matching unit 34 and a power feed rod 36. The high frequency power supply 32 applies a desired high frequency, for example, 60 MHz, to the lower electrode, that is, the susceptor 12. Facing the susceptor 12 in parallel, a shower head 38, which will be described later, is provided on the ceiling of the chamber 10 as an upper electrode of the ground potential. A high frequency electric field is formed in the space between the susceptor 12 and the shower head 38, that is, the plasma generation space PS by the high frequency from the high frequency power supply 32.

Here, the plasma generation space PS is not limited to a space radially inward from the outer peripheral ends of the susceptor 12 and the shower head 38, and spreads to a space radially outward from the outer peripheral ends of the susceptor 12 and the shower head 38 to the inner wall or side wall of the chamber 10. It is an extension. In the present invention, among the plasma generation space PS, it referred to the area PS _A radially inner than the outer peripheral edge of the substrate W placed on the susceptor 12 as a "main plasma region", outside clogging of "main plasma region" the radially outer region PS _B from the outer peripheral edge of the substrate W is referred to as a "peripheral plasma region".

  An electrostatic chuck 40 is provided on the upper surface of the susceptor 12 to hold the semiconductor wafer W with an electrostatic attraction force. The electrostatic chuck 40 has an electrode 40a made of a conductive film sandwiched between a pair of insulating films 40b and 40c, and a DC power source 42 is electrically connected to the electrode 40a via a switch 43. The semiconductor wafer W can be attracted and held on the chuck by a Coulomb force by a DC voltage from the DC power source 42.

  Inside the susceptor 12, for example, a refrigerant chamber 44 extending in the circumferential direction is provided. A coolant having a predetermined temperature, for example, cooling water is circulated and supplied to the coolant chamber 44 from the chiller unit 46 through the pipes 48 and 50. The processing temperature of the semiconductor wafer W on the electrostatic chuck 40 is controlled by the temperature of the coolant. Further, a heat transfer gas such as He gas from the heat transfer gas supply unit 52 is supplied between the upper surface of the electrostatic chuck 40 and the back surface of the semiconductor wafer W via the gas supply line 54.

  The shower head 38 at the ceiling includes an electrode plate 56 on the lower surface having a large number of gas vent holes 56a, and an electrode support 58 that detachably supports the electrode plate 56. A buffer chamber 60 is provided inside the electrode support 58, and a gas supply pipe 64 from the processing gas supply unit 62 is connected to a gas inlet 60 a of the buffer chamber 60.

In a ceiling portion of the chamber 10, above (preferably around the shower head 38) of the peripheral plasma region PS _B, the magnetic field forming mechanism 66 that extend annularly or concentrically are provided. The magnetic field forming mechanism 66 functions to facilitate the start of high-frequency discharge (plasma ignition) in the plasma generation space PS in the chamber 10 and maintain the discharge stably. The detailed configuration and operation of the magnetic field forming mechanism 66 will be described in detail later.

  The control unit 68 controls the operation of each unit in the plasma etching apparatus, such as the exhaust device 28, the high frequency power supply 32, the electrostatic chuck switch 43, the chiller unit 46, the heat transfer gas supply unit 52, and the processing gas supply unit 62. It is also connected to a host computer (not shown).

  In order to perform etching in this plasma etching apparatus, first, the gate valve 30 is opened, and the semiconductor wafer W to be processed is loaded into the chamber 10 and placed on the susceptor 12. Next, a DC voltage is applied from the DC power source 42 to the electrode 40 a of the electrostatic chuck 40 to fix the semiconductor wafer W on the electrostatic chuck 40. Then, an etching gas (generally a mixed gas) is introduced into the chamber 10 from the processing gas supply unit 62 at a predetermined flow rate and flow rate ratio, the pressure inside the chamber 10 is set to a set value by the exhaust device 28, and the high-frequency power source 32. A high frequency is supplied to the susceptor 12 with a predetermined power. The etching gas discharged from the shower head 38 is discharged into plasma in the plasma generation space PS, and the main surface of the semiconductor wafer W is etched by radicals and ions generated by the plasma.

In this plasma etching apparatus, a magnetic field forming mechanism 66 of the chamber ceiling forms a substantial magnetic field is limited to the peripheral plasma region PS _B of the plasma generation space PS. Thus, when the high frequency from the high frequency power source 32 is applied to the susceptor 12, the first etching gas starts to discharge in the peripheral plasma region PS _B in the presence of a magnetic field, from which the plasma generation space entire PS momentarily The discharge expands and a glow discharge or plasma generation is established. Thereafter, since the magnetic field assists or maintains the high frequency discharge in the peripheral plasma region PS _B , the discharge or plasma generation is stably maintained in the entire plasma generation space PS as long as the supply of the etching gas and the application of the high frequency are maintained. The

Here, the magnetic field works well for the initiation and maintenance of high-frequency discharge. Charge (mainly electrons) drifting under a high-frequency electric field receives a force (Lorentz force) by the magnetic field, and accelerates in the direction of the force. This is to increase the energy for ionizing gas molecules and atoms. In the peripheral plasma region PS _B , a high-frequency electric field is mainly formed between the inner wall (ceiling part and side wall) of the chamber 10 and the lower electrode 12.

In this manner, the magnetic field in the peripheral plasma region PS _B triggers the start of high-frequency discharge and assists the maintenance of the discharge, so that the discharge is performed even under the conditions of low gas pressure (for example, 10 mTorr or less), sandwiched electrode spacing, and low RF applied voltage. It is easy to start and keep the discharge stable. As an example, in the etching of polysilicon using HBr as a single gas as an etching gas, it has been difficult to start discharge (plasma ignition) when the gas pressure is 5 mtorr or less. According to this embodiment, the gas pressure is 5 mtorr. It has been confirmed that the discharge can be surely started and the discharge can be stably maintained even in the following.

On the other hand, the magnetic field forming mechanism 66 forms a substantially non-magnetic field state in the main plasma region PS _A. As a result, it is possible to avoid or reduce the possibility that a magnetic field acts on the semiconductor wafer W on the susceptor 12 to damage or stress the devices on the wafer. Here, the non-magnetic field state that does not damage or stress the device on the wafer is preferably a state below the geomagnetic level (for example, 0.5 G) in terms of magnetic field strength, but there is no problem even at about 5 G (substantially). May be said to be a typical magnetic field-free state).

2 and 3 show the configuration and operation of the magnetic field forming mechanism 66. FIG. As shown in FIG. 2, the magnetic field forming mechanism 66 includes a pair of magnetic field forming units [M _i , m _i ] with a pair of segment magnets M _i , m _i arranged in parallel at a constant interval in the chamber radial direction. Preferably, N sets (N is an integer of 2 or more) of magnetic field forming units [M ₁ , m ₁ ], [M ₂ , m ₂ ],..., [M _N , m _N ] are arranged in the circumferential direction. They are lined up at regular intervals.

In each magnetic field forming unit [M _i , m _i ], the segment magnet M _{i on the} outer side in the radial direction has a rectangular parallelepiped shape and is arranged with the N-pole surface facing downward. On the other hand, the segment magnets m _i of the radially inner has a rectangular parallelepiped shape is disposed toward the face of the S-pole downward. Both the segment magnets M _i, m _i may be constituted by permanent magnets such as rare earth magnets (samarium-cobalt magnet, neodymium magnet or the like).

According to such a magnetic pole arrangement structure, the magnetic lines of force B _i coming out from the lower surface (N pole) of the outer segment magnet M _i fall in the peripheral plasma region PS _B immediately below, and then turn upward to draw a parabola. was reached on the lower surface (S pole) of the inner segment magnets m _i with. Also in the adjacent magnetic field forming unit [M _{i + 1} , m _{i + 1} ], a predetermined angular interval in the circumferential direction from the magnetic field forming unit [M _i , m _i ] (for example, 15 ° when N = 24). Magnetic field lines B _{i + 1} having loops similar to those described above are formed at positions separated by a distance.

As shown in FIG. 3, the magnetic field forming units [M _i, m _i] On top of the back or top of the outer segment magnets M _i (S-pole) and the back or upper surface of the inner segment magnets m _i (N pole) Are provided for magnetically coupling the two. The back yoke structure, so most of the magnetic lines B _i emitted from the back (N pole) of the inner segment magnets m _i reaches the back of the outer segment magnets M _i through the inside of the yoke 70 (S pole) ing. The yoke 70 may be formed in a ring shape so as to cover all the magnetic field forming units [M ₁ , m ₁ ], [M ₂ , m ₂ ], ..., [M _N , m _N ].

As described above, in each magnetic field forming unit [M _i , m _i ], the magnetic field lines B _i coming out from the lower surface (N pole) of the outer segment magnet M _i fall into the peripheral plasma region PS _B immediately below and then move in all directions. point to reach the lower surface of the inner segment magnets m _i and U-turn upward without divergence (S pole) is important. Such magnetic field lines loop structure, at the same time enhances the magnetic flux density near the plasma region PS _B, it is possible to prevent the inflow of magnetic field lines in the main plasma region PS _A side effectively. To enhance effects of such magnetic field lines loop structure more, between the outer segment magnets M _i and the inner segment magnets m _i, relatively, magnetic charge of distant former M _i from the substrate G (the pole intensity) increased preferably, to reduce magnetic charge of the latter m _i closer to the substrate G (the pole strength).

Further, in this embodiment, each part (particularly, each magnetic field forming unit [M _i , m _i ]) of the magnetic field forming mechanism 66 is disposed above the peripheral plasma region PS _B , that is, radially inward from the side wall of the chamber 10. The point is also important. According to such a pole arrangement, as compared with the construction of arranging the magnetic field forming unit outside the sidewall of the chamber 10, because is much shorter radial distance and orbiting distance to the center of the chamber, the peripheral plasma region PS in _B The number of magnets or magnetic poles and magnetic quantity (proportional to size or volume) for forming a magnetic field having a suitable profile can be greatly reduced, and the apparatus size and cost associated with the installation of the magnetic field forming mechanism 66 can be reduced. Can be minimized. Here, the preferred profile of the magnetic field formed around the plasma region in PS _B, magnetic without affecting the main plasma region PS _A, a strong magnetic field as close as possible to the main plasma region PS _A obtained Profile.

4A and 4B show the magnetic field strength distribution in the plasma generation space PS according to one embodiment. In this embodiment, a 300 mm diameter semiconductor wafer is assumed as the substrate W to be processed, the inner diameter of the chamber 10 is set to about 260 mm, and the electrode interval (gap) is set to 25 mm. FIG. 4A shows the magnetic field strength distribution (average value in the circumferential direction) in the radial direction at the height position of the lower surface of the upper electrode 38 (electrode gap top position: Z = 25 mm). FIG. 4B shows the magnetic field strength distribution (average value in the circumferential direction) in the radial direction at the height position (electrode gap bottom position: Z = 0 mm) of the upper surface of the semiconductor wafer W placed on the susceptor 12. In the figure, the solid line shows the characteristic (example) obtained by the magnetic field forming mechanism 66 as described above, and the dotted line shows the characteristic (reference example) when each inner segment magnet _mi is omitted in the magnetic field forming mechanism 66.

As apparent from FIGS. 4A and 4B, in the reference example, the magnetic field lines B _i emitted from the lower surface (N pole) of the outer segment magnet M _i tend to diverge in all directions, so that the magnetic field remains in the peripheral plasma region PS _B. It not, also extends to the main plasma region PS _A. In contrast, in the embodiment, is absorbed by the inner segment magnets m _i and U-turn without diverging magnetic force lines B _i emitted from the lower surface (N pole) of the outer segment magnets M _i is the square as described above Therefore, the magnetic field remains in the peripheral plasma region PS in _B, almost falls short of the main plasma generation region PS _A. In fact, according to the magnetic field forming mechanism 66 of the embodiment, it is possible to attenuate the magnetic field strength to geomagnetism level (e.g. 0.5G) or less in the main plasma region PS _A. Further, a 40G~450G the peak value in the peripheral plasma region PS _B, it is possible to obtain a sufficient magnetic field strength to assist the discharge sustaining triggers the start of the high-frequency discharge.

  4A and 4B are at the gap top position between electrodes (Z = 25 mm) and the gap bottom position between electrodes (Z = 0 mm), but the intermediate portion between electrodes (0 mm <Z <25 mm). ), It will be easily understood that an intermediate magnetic field strength distribution between FIGS. 4A and 4B can be obtained.

As described above, in each magnetic field forming unit [M _i , m _i ], the magnetic field lines B _i coming out from the lower surface (N pole) of the outer segment magnet M _i fall into the peripheral plasma region PS _B immediately below and then move in all directions. point to reach the lower surface of the inner segment magnets m _i and U-turn upward without divergence (S pole) is important. Such magnetic field lines loop structure, at the same time enhances the magnetic flux density near the plasma region PS _B, it is possible to prevent the inflow of magnetic field lines in the main plasma region PS _A side effectively. To increase effects of such magnetic field lines loop structure more, between the outer segment magnets M _i and the inner segment magnets m _i, relatively, magnetic charge of distant former M _i from the substrate G (the pole intensity) increased preferably, to reduce magnetic charge of the latter m _i closer to the substrate G (the pole strength).

Another aspect of the present invention, the magnetic field in this embodiment, as described above, orthogonal to the periphery of the main plasma region PS _A extending in the vertical direction magnetic field (plasma diffusion directions surrounding like a curtain by the magnetic field forming mechanism 66 ) B can be formed. According to such a curtain-type vertical magnetic field B, can be schematically as shown, be confined effectively and efficiently to the inside without escaping the plasma PR in the main plasma region PS _A out in Figure 5 , and the balance the density and uniformity of the plasma PR in the main plasma region PS _a, it is possible to turn improve the plasma etching characteristics on the semiconductor wafer W.

For example, if the peripheral plasma region PS _B does not form a magnetic field, relatively etched in the wafer edge side with respect to the wafer center side as a dashed line ER _A of oxide-based Process (e.g. etching of the silicon oxide film) 5 tend to speed drops tend to relatively etch rate drops in the wafer center side with respect to the wafer edge side as shown by a dotted line ER _B poly-based processes (such as poly silicon etching) in Fig. By forming a curtain-type vertical magnetic field B in the peripheral plasma region PS _B by the magnetic field forming mechanism 66 as in this embodiment, the etching rate on the wafer edge side is made relative to the etching rate on the wafer center side in the oxide film process. to greatly up to improve in-plane uniformity as shown by the solid line ER _S, poly system in the process of the solid line ER _S with relatively greatly up the etch rate of the wafer center side with respect to the etching rate of the wafer edge side In-plane uniformity can be improved.

6 and 7 show a modification of the magnetic field forming mechanism 66 in this embodiment. In this modification, in the magnetic field forming mechanism 66, the magnetic field forming units [M ₁ , m ₁ ], [M ₂ , m ₂ ],..., [M _N , m _N ] are placed at the center of the chamber 10 (on the semiconductor wafer W). It is configured to rotate at a constant speed around a vertical line G passing through the center O). In the illustrated example, magnetic ring forming units [M ₁ , m ₁ ], [M ₂ , m ₂ ],..., Are connected to a ring-shaped internal gear 74 configured to be rotatable along a guide 72 via a yoke 70. [M _N , m _N ] is attached, and the rotational drive shaft of the electric motor 78 is connected to the internal gear 74 via the external gear 76. By such a rotating magnetic field mechanism, the magnetic field strength distribution can be made uniform in the circumferential direction even if the number of magnetic field forming units [M _i , m _i ] is small. In particular, when a deposited film adheres to the chamber ceiling directly below the magnetic field forming mechanism 66 due to the action of a vertical magnetic field, the degree of deposition film thickness and film thickness are made uniform in the circumferential direction by making the magnetic field strength distribution uniform. Can be

8 and 9 show another embodiment of the magnetic field forming mechanism 66. FIG. In this embodiment, one or a plurality of magnets <M _i > are disposed above the peripheral plasma region PS _B (preferably the chamber ceiling around the shower head 38), and below the peripheral plasma region PS _B , for example, exhaust A magnetic body K is disposed near the path 20 or the baffle plate 22. In the configuration example of FIG. 8, the magnetic body K is attached to the cylindrical support portion 16 in the exhaust passage 20, and in the configuration example of FIG. 9, the magnetic body K is attached to the chamber side wall portion in the exhaust passage 20. The magnet <M _i > may correspond to, for example, the outer segment magnet M _i in FIGS. 2 to 7, and is arranged with the N-pole surface facing downward, for example. The magnetic body K may be one in which a plurality of segment magnetic bodies are arranged at regular intervals in the circumferential direction, or may be made of a single ring-shaped magnetic body, and the material is metal, ferrite, ceramic, etc. Any of these may be used.

According to such a magnetic pole arrangement structure, the magnetic lines of force B _i emitted from the lower surface (N pole) of the magnet <M _i > reach the magnetic body K across the immediate peripheral plasma region PS _B from top to bottom. Magnetic K is magnetized by receiving the magnetic field lines B _i, its surface becomes an S pole. 8 and 9, the yoke 80 surrounding the back surface (upper surface) and the side surface of the magnet <M _i > in order to direct the magnetic field lines B _i from the magnet <M _i > to the magnetic body K as much as possible. Provided. In particular, the main plasma region PS _A side of the side yoke portion 80a has an upper surface or rear surface of the magnet <M _i> captures the magnetic force lines leaving the main plasma region PS _A side from the lower surface of the magnet <M _i> (N-pole) ( is fed back to the S pole), there acts to not to go to the main plasma region PS _a.

8 and 9, the upper and lower polarities of the magnet <M _i > are reversed so that the lower surface is the south pole, and the arrangement positions of the magnet <M _i > and the magnetic body K are interchanged with each other. Deformation and the like are possible. In addition, although the number of magnets <M _i > and the volume increase and the size of the apparatus are increased, it is possible to arrange the magnets <M _i > outside the side walls of the chamber 10 as shown in FIG. . Alternatively, a configuration in which the magnet <M _i > is disposed inside the sidewall of the chamber 10 and the magnetic body K is disposed outside the chamber sidewall is also possible.

Various modifications are also possible in the embodiment of FIGS. For example, in each of the magnetic field forming units [M _i, m _i], the polarity of the upper and lower vertical polarity and the inner segment magnets m _i of the outer segment magnets M _i respectively is inverted, the lower surface of the outer segment magnets M _i S pole and then, a configuration is possible in which the lower surface of the inner segment magnets m _i and N pole. It is also possible to substitute one segment magnet (usually the inner segment magnet _mi ) with a magnetic material. Further, the magnetic field forming unit [M _i , m _i ] is arranged below the peripheral plasma region PS _B , for example, one side (M _i ) is attached to the susceptor 12 side and the other side (m _i ) is attached to the side wall of the chamber 10. It is also possible to have a configuration that is attached to the battery. Furthermore, it an enlargement of the number increases and volume increases and hence apparatus magnet companion, but can also be configured to place the outside of the side wall of the chamber 10 the outer segment magnets M _i, as shown in FIG. 11. Further, in each magnetic field forming unit [M _i , m _i ], a configuration in which both magnets M _i and m _i are arranged in a direction other than the radial direction is also possible.

  The parallel plate type plasma etching apparatus (FIG. 1) in the above embodiment is a system in which one high frequency power for plasma generation is applied to the susceptor 12. However, although not shown in the drawings, the present invention applies a method of applying high-frequency power for plasma generation to the upper electrode 38 side, and applies first and second high-frequency powers having different frequencies to the upper electrode 38 and the susceptor 12, respectively. It can also be applied to a method (upper and lower high-frequency application type) and a method of applying first and second high-frequency powers having different frequencies to the susceptor 12 (lower two-frequency superimposed application type). The present invention is applicable to a plasma processing apparatus having at least one electrode in a possible processing container. Of course, the present invention and the ignition plasma method can be used in combination.

  The plasma source to which the present invention can be applied is not limited to the parallel plate type, but may be any other high-frequency discharge method, for example, a helicon wave plasma method. Furthermore, the present invention can also be applied to other plasma processing apparatuses such as plasma CVD, plasma oxidation, plasma nitridation, and sputtering. Further, the substrate to be processed in the present invention is not limited to a semiconductor wafer, and various substrates for flat panel displays, photomasks, CD substrates, printed substrates, and the like are also possible.

10 Chamber 12 Susceptor (lower electrode)
20 Exhaust path 28 Exhaust device 32 High frequency power supply 38 Shower head (upper electrode)
62 Process gas supply unit 66 Magnetic field forming mechanism 70 Yoke 78 Electric motor 80 Yoke M _i outer segment magnet m _i outer segment magnet <M _i > magnet

Claims (11)

A plasma processing method of flowing a processing gas into a chamber capable of depressurization and generating a plasma of the processing gas by forming a high-frequency electric field, and performing a desired plasma processing on a substrate to be processed under the plasma,
Of the plasma generation space in the chamber, the magnetic lines of force pass only in the peripheral plasma region radially outside the outer peripheral edge of the substrate, and both the starting and ending points of the magnetic lines of force are from the side wall of the chamber. Also forms a magnetic field that is located radially inside,
In the magnetic field, both the starting point and the ending point of the magnetic lines of force are located above the peripheral plasma region, and the magnetic lines of force emitted from the starting point make a U-turn in or below the peripheral plasma region to reach the end point,
Both the first and second magnetic poles that respectively provide the starting point and the ending point of the magnetic field lines are magnets, and the amount of magnetic force arranged radially outward is between the first and second magnetic poles in the radial direction. Larger than the amount of magnetism on the inside,
In the plasma generation space, in the main plasma region radially inward from the outer peripheral edge of the substrate, a substantially no magnetic field state is set.
Plasma processing method. A depressurizable chamber;
An electrode for placing the substrate to be processed substantially horizontally in the chamber;
A processing gas supply unit for supplying a processing gas to a plasma generation space set above and around the electrode;
A high-frequency electric field forming mechanism for forming a high-frequency electric field in the plasma generation space;
Of the plasma generation space in the chamber, the magnetic lines of force pass only in the peripheral plasma region radially outside the outer peripheral edge of the substrate, and both the starting and ending points of the magnetic lines of force are from the side wall of the chamber. Has a magnetic field formation mechanism that forms a magnetic field located radially inward,
The magnetic field forming mechanism is arranged such that both the first and second magnetic poles face downward and above the peripheral plasma region;
In the magnetic field, the magnetic field lines coming out of the first magnetic pole at the starting point descend into the peripheral plasma region and then make a U-turn to reach the second magnetic pole at the end point,
Both the first and second magnetic poles that respectively provide the starting point and the ending point of the magnetic field lines are magnets, and the amount of magnetic force arranged radially outward is between the first and second magnetic poles in the radial direction. Larger than the amount of magnetism on the inside,
In the plasma generation space, in the main plasma region radially inward from the outer peripheral edge of the substrate, a substantially no magnetic field state is set.
Plasma processing equipment.   The plasma processing apparatus according to claim 2, wherein one of the first and second magnetic poles is an N pole and the other is an S pole.   The plasma processing apparatus according to claim 2, wherein the first and second magnetic poles are provided in a ceiling wall of the chamber.   In the magnetic field, a part of the lines of magnetic force coming out of the first magnetic pole at the starting point descends into the peripheral plasma region, and makes a U-turn at a lower position than the substrate to make the second magnetic pole at the end point. The plasma processing apparatus as described in any one of Claims 2-4 which reaches | attains.   The intensity of the magnetic field in the peripheral plasma region becomes maximum and maximum at a certain position between the outer peripheral edge of the substrate and the side wall of the chamber in the radial direction of the chamber. The plasma processing apparatus according to one item.   The plasma processing apparatus according to claim 2, wherein the first magnetic pole and the second magnetic pole are juxtaposed at a desired interval in the radial direction of the chamber.   The plasma processing apparatus according to claim 2, wherein a large number of the first and second magnetic poles are arranged at predetermined intervals in the circumferential direction.   The plasma processing apparatus according to claim 2, further comprising a magnetic pole rotating unit that rotates the first and second magnetic poles integrally in a circumferential direction.   The plasma processing apparatus according to any one of claims 2 to 9, wherein a yoke is provided in contact with or in proximity to the back surface of the magnet as viewed from the peripheral plasma region side.   The plasma processing apparatus according to claim 10, wherein a yoke is provided in contact with or close to a side surface of the magnet near the main plasma region.

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