JPWO2014199421A1 - Plasma generating apparatus, plasma processing apparatus, plasma generating method and plasma processing method - Google Patents

Abstract

Provided is a plasma generation device capable of substantially eliminating sputtering of member materials such as electrodes existing around a plasma excitation region by accelerated electrons. An electrode (10) for plasma formation having a main surface (10a) and a back surface (10b), a high-frequency supply unit (100, 70, 60) for supplying high-frequency power having a frequency of 200 MHz or more to the electrode (10), an electrode A first fixed magnet (56) provided on the back side of (10) and having a north pole opposed to the back and a second fixed magnet (58) having a south pole opposed to the back; And a magnetic field forming mechanism (50) for forming a looped magnetic field region LMR for confining the excited plasma near the main surface (10a), and the looped magnetic field region formed by the magnetic field forming mechanism (50) The LMR has a strong magnetic field of 3000 gauss or more in a direction parallel to the main surface (10a).

Description

  The present invention relates to a plasma generation apparatus, a plasma processing apparatus using the plasma generation apparatus, a plasma generation method, and a plasma processing method using the plasma generation method.

  Plasma processing processes such as plasma CVD (Chemical Vapor Deposition) require plasma with a low electron temperature in order to reduce ion irradiation damage by suppressing ion irradiation energy incident on the surface of a substrate such as a silicon wafer. . In general, when the plasma excitation frequency is increased, the plasma density increases and the electron temperature decreases. Therefore, a high frequency of a VHF (Very High Frequency) band of 30 to 300 MHz, which is higher than a frequency of 13.56 MHz, which is a frequency of a normal high frequency power source, is used for plasma processing (for example, see Patent Documents 1 and 2).

JP-A-9-31268 JP 2009-021256 A

  For example, in the microwave plasma technology, if the plasma excitation frequency is increased as described above, the ion irradiation energy in the diffusion plasma region where the excited plasma diffuses can be sufficiently reduced, and the ion irradiation damage of the silicon wafer can be reduced. We are at a stage where we can almost eliminate. However, in the plasma excitation region, electrons are accelerated by a strong microwave electric field, so that the ion irradiation energy rises to several tens of eV. As a result, the accelerated electrons cause sputtering of the member material existing around the plasma excitation region such as the electric field forming electrode and the inner wall surface of the processing chamber, and the sputtered material adheres to the silicon wafer. Nation occurs.

  The object of the present invention is to reduce the electron temperature of the plasma to such an extent that ion irradiation damage to the object to be processed such as a silicon wafer can be eliminated. It is an object of the present invention to provide a plasma generation apparatus and method capable of substantially eliminating sputtering by accelerated electrons. Another object of the present invention is to provide a plasma processing apparatus and method using the plasma generating apparatus and method.

  The plasma generator of the present invention includes a plasma forming electrode having a main surface and a back surface opposite to the main surface, and a high frequency supply unit that supplies high frequency power having a frequency of 200 MHz or more to the plasma forming electrode. A first fixed magnet provided on the back side of the electrode and having an N pole opposed to the back surface and a second fixed magnet having an S pole opposed to the back surface, the first fixed magnet Using a magnetic field line that exits from the N pole of the magnet and passes through the electrode and enters the S pole of the second fixed magnet, a loop-shaped magnetic field region is formed to confine excited plasma near the main surface. A loop-shaped magnetic field region formed by the magnetic field forming mechanism has a strong magnetic field of 3000 gauss or more in a direction parallel to the main surface.

  The plasma processing apparatus of the present invention is a plasma processing apparatus that performs plasma processing on an object to be processed that is disposed to face the main surface of the electrode by using the plasma generator, and the electrode should be converted into plasma. A source gas supply unit for supplying source gas to the loop-shaped magnetic field region is provided in a region corresponding to the loop-shaped magnetic field region.

  The plasma generation method of the present invention supplies a high frequency power having a frequency of 200 MHz or more to a plasma forming electrode having a main surface and a back surface opposite to the main surface, and is provided on the back surface side of the electrode. From the N pole of the first fixed magnet using a magnetic field forming mechanism including a first fixed magnet having a pole opposed to the back surface and a second fixed magnet having an S pole opposed to the back surface. Using a magnetic field line that passes through the electrode and enters the south pole of the second fixed magnet, a loop-shaped magnetic field region for confining the excited plasma near the main surface is formed, and the loop-shaped magnetic field region is formed. The loop-shaped magnetic field region is formed so that the magnetic field region has a strong magnetic field of 3000 gauss or more in a direction parallel to the main surface.

  The plasma processing method of the present invention is a plasma processing method of performing plasma processing on an object to be processed that is disposed to face the main surface of the electrode by using the plasma generation method described above, wherein the loop shape of the electrode is A material gas to be converted into plasma is supplied to the loop-shaped magnetic field region from a material gas supply unit provided in a region corresponding to the magnetic field region.

  In the present invention, plasma is excited by supplying high-frequency power having a frequency of 200 MHz or more to an electrode for plasma formation, and the excited plasma is confined in a looped magnetic field region formed on the main surface of the electrode. And, by making the loop magnetic field region have a strong magnetic field of 3000 gauss or more in the direction parallel to the main surface, it is possible to further increase the plasma density by strongly winding the plasma around the lines of magnetic force, As a result, the electron temperature of the confined plasma can be lowered to such an extent that a member such as a plasma forming electrode disposed around the plasma excitation region is not sputtered.

1 is a cross-sectional view schematically showing a plasma processing apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view in a circle IIA in FIG. 1. The figure which shows the arrangement | sequence of the gas supply hole of a shower plate. The top view which shows the structure of the magnetic field formation mechanism of the apparatus of FIG. The top view which shows the other example of a magnetic field formation mechanism. The top view which shows the further another example of a magnetic field formation mechanism. Sectional drawing which shows the relationship between a fixed magnet and a loop-shaped magnetic field area | region. The graph which shows horizontal magnetic field strength distribution of the loop-shaped magnetic field area | region formed in a main surface. Sectional drawing of the VI-VI line of FIG. 1 which shows the structure of an electric power feeding part.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  Here, the basic principle of the present invention will be described. In the present invention, in order to remove damage caused by ion irradiation of an object to be processed such as a silicon wafer, the conventional plasma excitation frequency is increased. In addition to this, the confinement effect by the magnetic field is utilized to convert the supplied high frequency power into energy for increasing the plasma density, not for accelerating the plasma. Here, the inventors of the present invention set the magnetic field region for confining the plasma to a magnetic field in which the intensity of a magnetic field in a direction parallel to the main surface of the electrode (hereinafter referred to as a horizontal magnetic field) is 3000 gauss or more. As a result, the plasma confinement effect is improved by strongly wrapping the plasma around the magnetic field lines, the plasma density is increased, and the electron temperature of the plasma in the plasma excitation region is substantially reduced by the sputtering of the electrode for forming the plasma and the surrounding members. It was newly found that it can be lowered to the extent that it does not occur. An increase in plasma density means that the input high frequency power is consumed for increasing the plasma density, and the electron temperature of the plasma is decreased. The plasma generator of the present invention is not limited to this, but can also be referred to as a “horizontal high magnetic field application high frequency excitation plasma apparatus”.

  As shown in FIG. 1, a plasma processing apparatus according to the present embodiment (hereinafter referred to as apparatus 1) is used for various plasma processes such as plasma CVD (Chemical Vapor Deposition), for example. The apparatus 1 includes a metal processing chamber 200 that defines a sealed space 201, a stage 220 for mounting a substrate W such as a silicon wafer formed from aluminum nitride or the like installed in the processing chamber 200, The plasma forming electrode 10 provided above, the magnetic field forming mechanism 50 installed on the electrode 10, the power supply unit 60 electrically connected to the electrode 10, and the matching unit 70 provided on the upper lid 202 of the processing chamber 200. And a power supply 100. The stage 220 can rotate the substrate W about the rotation axis C.

  The processing chamber 200 is made of a conductive material such as aluminum alloy or stainless steel, and is connected to a reference potential. An exhaust port 205 for exhausting the atmosphere in the processing chamber 200 is provided at the bottom of the processing chamber 200, and an exhaust device such as a vacuum pump (not shown) installed outside the processing chamber 200 is connected to the exhaust port 205. Is done. With this exhaust device, the sealed space 201 is depressurized.

The electrode 10 is formed of a conductive plate-like member, and is formed of a nonmagnetic material, for example, an aluminum alloy having an anodized film formed on the surface. The electrode 10 is held by a holding member 80 having an outer peripheral portion formed of an insulator such as aluminum oxide, and includes a main surface 10a formed of a plane on the side facing the stage 220 and a back surface 10b opposite to the main surface 10a. Yes. The holding member 80 is fixed to the upper part of the processing chamber 200, is sealed with an O-ring 82 between the electrode 10, and is sealed with an O-ring 84 with the processing chamber 200. As shown in FIG. 2A, the electrode 10 is formed with grooves 11 for embedding fixed magnets 56 and 58 (to be described later) of the magnetic field forming mechanism 50 on the back surface 10b, and on the main surface 10a side, for example, SiH ₄ , N ₂ , a gas flow path 12 for supplying a source gas such as O ₂ and N ₂ O is formed, and a cooling water flow path 14 through which cooling water for preventing overheating of the electrode 10 passes is formed. . On the main surface 10a side of the gas flow path 12, a shower plate 20 is provided integrally with the electrode 10 so as to be flush with the main surface 10a. That is, the surface of the shower plate 20 constitutes a part of the main surface 10a. The shower plate 20 is made of the same material as the electrode 10. A large number of gas supply holes 21 are formed in the shower plate 20, and the gas supply holes 21 are arranged as shown in FIG. 2B. For example, the hole diameter is 0.2 mm, the pitch is 0.5 mm, the pressure is 500 mTorr, and the gas Gas can be supplied under conditions of a flow rate of 1000 sccm or a gas flow rate of 5 m / s. The arrangement of the shower plate 20 will be described later.

  The magnetic field forming mechanism 50 includes a yoke 52 formed in a flat plate shape, and a magnet 56 as a first fixed magnet and a magnet 58 as a second fixed magnet provided on the lower surface of the yoke 52. The yoke 52 is made of iron, and the surface other than the lower surface is covered with a conductive cover 53 made of aluminum alloy or the like. This is to prevent this by covering the yoke 52 with a low-resistance material such as an aluminum alloy because energy loss due to heat generation occurs when a high-frequency current flows through the iron yoke 52 having a relatively high resistance.

  The magnets 56 and 58 are plate-shaped magnets, and in order to stably generate a strong magnetic field, the residual magnetic flux density, coercive force, energy of Sm—Co based sintered magnet, Nd—Fe—B based sintered magnet, etc. High product magnets are used. The magnets 56 and 58 are embedded in the groove 11 formed on the back side of the electrode 10 shown in FIG. 2A. The surfaces of the magnets 56 and 58 are covered with an insulating material such as a fluorocarbon resin (trade name: Teflon (registered trademark)), and the electrode 10 and the magnets 56 and 58 are electrically insulated. Yes. Each magnet 56, 58 is magnetized in a direction perpendicular to its surface. The magnets 56 are arranged so that the north pole faces the back surface 10b of the electrode 10, and extends in the Y-axis direction and is arranged at equal intervals in the X-axis direction as shown in FIG. 3A. The magnet 58 has a south pole facing the back surface 10b of the electrode 10, is disposed between two adjacent magnets 56, and has a plurality of longitudinal portions 58a along the Y-axis direction, and both ends of the plurality of longitudinal portions 58a. It consists of the connection part 58b which connects a part mutually. A certain gap is formed between the magnet 56 and the longitudinal portion 58 a of the magnet 58. A certain gap is also formed between the magnet 56 and the connecting portion 58 b of the magnet 58. In FIG. 3A, the widths of the two longitudinal portions 58a at both ends in the X-axis direction are narrower than the widths of the other longitudinal portions 58a. The magnet 56 has dimensions of, for example, a width of 20 mm and a length of 330 mm. The magnet 58 has, for example, an overall width in the X-axis direction of 410 mm, an overall width in the Y-axis direction of 390 mm, and the width of the longitudinal portion 58a other than both ends. 20 mm, the width of the longitudinal portion 58 a at both ends is 15 mm, and the width of the connecting portion 58 b is 10 mm.

  Here, as schematically shown in FIG. 4, a part MFL of the lines of magnetic force emerging from the north pole of the magnet 56 is such that the north pole of the magnet 56 and the south pole of the magnet 58 are adjacent to each other. , Passes through the main surface 10a of the electrode 10, passes through the electrode 10 again, and enters the south pole of the adjacent magnet 58. The magnetic lines of force MFL are formed around the entire circumference of the magnet 56, whereby a loop-shaped magnetic field region LMR for confining the excited plasma in the vicinity of the main surface 10a is formed in the region indicated by the dotted line in FIG. In the present invention, the magnetic field forming mechanism 50 is configured so that the magnetic field region LMR has a strong magnetic field of 3000 gauss or more in a direction parallel to the main surface 10a. A magnetic field in a direction parallel to the main surface 10a is called a horizontal magnetic field. The graph of FIG. 5 shows the intensity distribution of the horizontal magnetic field on the X axis at a position 8 mm away from the principal surface 10a of the electrode 10 in the vertical direction. The magnetic field region LMR is formed in a region where the horizontal magnetic field strength exceeds 3000 gauss. The width of the loop magnetic field region LMR is, for example, about 10 mm. The shower plate 20 described above is provided at a position facing the loop-shaped magnetic field region LMR. As a result, the source gas to be converted into plasma can be directly supplied to the loop-shaped magnetic field region LMR.

  The power supply 100 supplies high-frequency power of 200 MHz or more through the coaxial cable 101 to the electrode 10 through the matching unit 70 and the power feeding unit 60. In this embodiment, high frequency power of 200 MHz is supplied. The power feeding unit 60 includes a power receiving rod 66 electrically connected to the matching unit 70, a conductive plate 62 electrically connected to the power receiving rod 66, a power feeding rod 68 electrically connected to the conductive plate 62, and a phase. An adjustment plate 64 is provided. As shown in FIG. 6, the conductive plate 62 has a power receiving rod 66 connected to the central portion thereof and first and second branch portions 62 a and 62 b that branch in eight directions from the central portion. One end of a power feed rod 68 is connected to the tip of each of the first and second branch portions 62a and 62b. The other end of the power feeding rod 68 is electrically connected to the back surface 10 b of the electrode 10. The power receiving rod 66 and the conductive plate 62 are made of, for example, a copper alloy, and the power feeding rod 68 is made of, for example, an aluminum alloy. The four first branch portions 62a have an electrically equal length, and the four second branch portions 62a have an electrically equal length and are shorter than the first branch portion 62a. The phase adjustment plate 64 is formed of a dielectric such as quartz, and is provided on the four second branch parts 62a. The phase adjustment plate 64 is provided to adjust the phase of the high-frequency power supplied to the second branch portion 62b and to supply the high-frequency power having the same phase to the feeding rods 68 provided at eight locations.

  In the apparatus 1, when 200 MHz high frequency power is supplied to the electrode 10 through the matching unit 70 and the power feeding unit 60, plasma is excited in the vicinity of the main surface 10 a of the electrode 10. Since the loop-shaped magnetic field region LMR is formed on the plasma excitation region in the vicinity of the main surface 10a, particularly on the shower plate 20, the excited plasma is transferred to the surface of the shower plate 20 by the loop-shaped magnetic field region LMR. It is confined in the vicinity and moves along the loop. The source gas supplied from the gas supply hole 21 of the shower plate 20 is turned into plasma. At this time, by setting the horizontal magnetic field strength of the loop magnetic field region LMR to 3000 gauss or more, the plasma is strongly wound around the magnetic lines of force, the plasma confinement effect is improved, and the plasma density is increased. As a result, it has been found that the electron temperature of the plasma confined in the magnetic field region LMR can be lowered to such an extent that sputtering of the electrode 10, members disposed around the electrode 10 and the inner wall surface of the processing chamber 200 does not substantially occur. . Thus, it was found that the sputtered material does not adhere to the substrate W to be plasma-treated, and the film formation quality can be improved.

  In the present embodiment, as described above, the substrate W on the stage 220 is rotatable about the rotation axis C. At this time, as shown in FIG. 3A, when the center of the disk-shaped substrate W is decentered by about 10 mm with respect to the rotation axis C and rotated, for example, the disk-shaped substrate W moves within the region of the circle MW. Thereby, even if the magnetic field region LMR is formed in a vertically long loop shape, the uniformity of the film formed on the substrate W can be ensured.

  Although the case where the magnets 56 and 58 of the magnetic field forming mechanism 50 are arranged in a ladder shape has been described in the above embodiment, the present invention is not limited to this. Any configuration can be adopted as long as it can form a strong magnetic field of 3000 gauss or more. For example, as shown in FIG. 3B, cylindrical magnets 56A and annular magnets 56B and 56C are arranged concentrically as the first fixed magnets, and annular magnets 58A and 58B are magnets 56A as the second fixed magnets. It is also possible to employ a configuration in which the magnet 56B and the magnet 56C are disposed. Further, as shown in FIG. 3C, a magnet 156 (156a, 156b) as a first fixed magnet and a magnet 158 as a second fixed magnet are made of an insulator 59 (59a, 59b) such as aluminum oxide. It is also possible to separate them. Specifically, insulators 59a and 59b are inserted between the plurality of magnets 156a, between the magnets 156a and 156b, and between the plurality of magnets 158.

  In the above embodiment, plasma CVD is exemplified as the plasma processing. However, the present invention is not limited to this and can be applied to other plasma processing such as plasma etching.

  In the above embodiment, the case where the plasma generator of the present invention is used for plasma processing has been described. However, the present invention is not limited to this, and the plasma has a low electron temperature and a high density so as not to sputter an electrode or the like. It can be applied to situations where the occurrence of

  As mentioned above, although embodiment of this invention was described in detail, referring an accompanying drawing, this invention is not limited to this example. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 10 Electrode 10a Main surface 10b Back surface 20 Shower plate 21 Gas supply hole 50 Magnetic field formation mechanism 56 Magnet (1st fixed magnet)
58 Magnet (second fixed magnet)
70 Matching Device 100 Power Supply 200 Processing Chamber LMR Loop-shaped Magnetic Field MFL Magnetic Field Line PL Plasma

Claims (4)

An electrode for plasma formation having a main surface and a back surface opposite to the main surface;
A high-frequency supply unit that supplies high-frequency power having a frequency of 200 MHz or more to the plasma forming electrode;
A first fixed magnet provided on the back side of the electrode and having a north pole facing the back surface and a second fixed magnet having a south pole facing the back surface; A magnetic field that forms a loop-shaped magnetic field region for confining the excited plasma in the vicinity of the main surface by using magnetic field lines that exit from the N-pole and pass through the electrode and enter the S-pole of the second fixed magnet. A forming mechanism,
A loop-shaped magnetic field region formed by the magnetic field forming mechanism has a strong magnetic field of 3000 gauss or more in a direction parallel to the main surface. A plasma processing apparatus that uses the plasma generator according to claim 1 to perform plasma processing on an object to be processed that is disposed to face the main surface of the electrode.
The plasma processing apparatus, wherein the electrode includes a source gas supply unit for supplying source gas to be converted into plasma to the loop-shaped magnetic field region in a region corresponding to the loop-shaped magnetic field region. A high frequency power having a frequency of 200 MHz or more is supplied to a plasma forming electrode having a main surface and a back surface opposite to the main surface,
Using a magnetic field forming mechanism that is provided on the back side of the electrode and includes a first fixed magnet having a north pole facing the back and a second fixed magnet having a south pole facing the back. A loop shape for confining the excited plasma near the main surface by using magnetic lines that exit from the N pole of the first fixed magnet and pass through the electrode and enter the S pole of the second fixed magnet. Forming a magnetic field region,
Forming the loop-shaped magnetic field region so that the loop-shaped magnetic field region has a strong magnetic field of 3000 gauss or more in a direction parallel to the main surface;
A plasma generation method characterized by the above. Using the plasma generation method according to claim 3, a plasma processing method for plasma-treating an object to be processed that is disposed to face the main surface of the electrode,
A plasma processing method, comprising: supplying a source gas to be plasmified to a looped magnetic field region from a source gas supply unit provided in a region corresponding to the looped magnetic field region of the electrode.

Images