JP4305141B2 - Microwave introduction apparatus and surface wave excitation plasma processing apparatus - Google Patents

Description

  The present invention relates to a microwave introduction device that introduces microwaves from a microwave generation device into a plasma processing chamber, and a surface wave excitation plasma processing device that performs CVD, etching, and the like using surface wave excitation plasma.

  In a semiconductor manufacturing process, a plasma processing apparatus that uses plasma to perform CVD film formation, etching, or the like is used. As such a plasma processing apparatus, a parallel plate type plasma processing apparatus, an electron cyclotron resonance (ECR) plasma processing apparatus, and the like are conventionally used. Furthermore, in recent years, a surface wave plasma (SWP) plasma processing apparatus that can easily generate a plasma having a larger area has been used. The SWP plasma processing apparatus introduces microwave power from a slot antenna provided in a microwave waveguide into a plasma generation chamber via a dielectric member, and processes in the plasma generation chamber by surface waves generated on the surface of the dielectric member A gas is excited to generate surface wave excitation plasma, and an object to be processed is processed using the plasma.

  As the shape of the microwave waveguide, there are a linear shape and an annular shape, and they are properly used according to the shape of the object to be processed and the purpose of processing. The microwave introducing device using the annular waveguide has an advantage that the microwave can be introduced into the plasma generation chamber relatively uniformly. As this type of microwave introducing device, an endless annular waveguide in which a plurality of slot antennas are formed is known (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 5-345882 (2nd page, FIGS. 6 and 9)

  Since the endless annular waveguide of Patent Document 1 does not have a termination, microwave power may concentrate on a specific slot antenna. When this endless annular waveguide is used in a SWP plasma processing apparatus, there is a problem that the plasma density is localized at a specific portion of the dielectric member, causing damage to the object to be processed or non-uniform processing. .

(1) A microwave introduction device according to a first aspect has an introduction port for introducing a microwave from a microwave generation device and a termination portion, and a bottom plate on which a plurality of slot antennas are formed at predetermined intervals is an inner surface. Annular microwave waveguide and cylindrical shape, the outer surface of which is in contact with the bottom plate of the annular microwave waveguide, and introduces microwaves propagating through the annular microwave waveguide through the slot antenna And a cylindrical waveguide member that surrounds the cylindrical dielectric member along the microwave propagation direction, where λg is the in-tube wavelength of the microwave and a constant k is in the range of 0.95λg to λg. the length of the center line of the tube, while set to an integral multiple of the constant k, a predetermined distance of a plurality of slot antenna is set to an integral multiple of the constant k, a plurality of slot antenna, the microwave guide A first slot antenna group formed in the vicinity of the center of the bottom plate of the microwave waveguide and a second slot antenna group formed in the vicinity of the periphery of the bottom plate of the microwave waveguide with respect to the core wire; The first slot antenna group and the second slot antenna group are arranged in parallel while being shifted in position by an integral multiple of k / 4 in the direction of the center line of the microwave waveguide .

(2) The invention of claim 2 is characterized in that, in the microwave introduction device of claim 1 , a termination matching unit is provided at each termination portion of the microwave waveguide.

(3) According to a third aspect of the present invention, there is provided a surface wave excitation plasma processing apparatus, comprising: a microwave generation apparatus that generates a microwave; a microwave introduction apparatus according to the first or second aspect; And a processing chamber for generating surface wave excited plasma in an airtight space by microwaves introduced through a cylindrical dielectric member and processing an object to be processed by the surface wave excited plasma. .

  ADVANTAGE OF THE INVENTION According to this invention, the microwave introduction apparatus which can introduce a microwave into a plasma processing chamber uniformly, and the SWP plasma processing apparatus which can perform the uniform process without a plasma damage can be provided.

Hereinafter, a microwave introduction apparatus and a surface wave excitation plasma processing apparatus (hereinafter referred to as SWP processing apparatus) according to the present invention will be described with reference to FIGS.
<First Embodiment>
FIG. 1 is an overall configuration diagram schematically showing a SWP processing apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a main part of the SWP processing device according to the first embodiment. FIG. 3 is a cross-sectional view taken along the line II of FIG. 2 and is a plan view showing the configuration of the microwave introduction unit.

  Referring to FIGS. 1 and 2, the SWP processing apparatus 100 includes a microwave generation unit 1, a casing 2, and a microwave introduction unit 10. The microwave introduction unit 10 includes an annular waveguide 3 that propagates microwaves, and a cylindrical dielectric tube 4 that is incorporated in a side surface of the housing 2 and introduces microwaves into the housing 2. The housing 2 holds an upper gas introduction pipe 6 for introducing a process gas from the upper surface, a side gas introduction pipe 7 for introducing a material gas or a process gas from the side, a vacuum exhaust pipe 8 and a substrate S to be processed. A substrate holder 9 is provided.

  The microwave generation unit 1 includes a microwave power source 11, a microwave oscillator 12, an isolator 13, a directional coupler 14, and a matching unit 15. The microwave generator 1 generates a 2.45 GHz microwave and sends it to the inlet 3 a of the annular waveguide 3.

  The annular waveguide 3 is an annular microwave waveguide made of, for example, aluminum alloy or nonmagnetic stainless steel and having a bottom plate 3d as an inner surface. A plurality of slot antennas 5 are formed on the bottom plate 3d of the annular waveguide 3 at a predetermined interval. The inner surface of the bottom plate 3d is a surface called a magnetic field surface (H surface). A termination matching unit 3c for changing the termination position is provided at the termination portion 3b of the annular waveguide 3.

The dielectric tube 4 is made of quartz, alumina, or the like, and is attached to the housing 2 via O-rings 2a at both end faces, and the outer surface of the dielectric tube 4 is attached to the bottom plate 3d of the annular waveguide 3. It is arranged in contact. Thereby, an airtight space is formed in the housing 2. While introducing a process gas such as N ₂ gas, H ₂ gas, O ₂ gas, Ar gas or a material gas such as SiH ₄ gas or Si ₂ H ₆ gas from the top gas introduction pipe 6 and the side gas introduction pipe 7, a vacuum By exhausting through the exhaust pipe 8, the inside of the housing 2 is maintained at a predetermined pressure. As will be described later, microwave power is introduced from the annular waveguide 3 into the dielectric tube 4 to generate plasma in the internal space of the housing 2.

With reference to FIG. 3, the structure of the microwave introduction part 10 is demonstrated in detail. When the center line along the microwave propagation direction of the annular waveguide 3 is denoted by CL1, and the length of the center line CL1 surrounding the dielectric tube 4 is denoted by L1, the length L1 is from the start point A to the end point B. Distance. The start point A is in the vicinity of the microwave M introduction port, and the end point B is separated from the end point E1 by a distance b1. The slot antennas 51 to 58 are long rectangular openings formed at predetermined intervals along the microwave propagation direction of the annular waveguide 3.
Hereinafter, for the sake of simplicity, the annular waveguide 3 and the dielectric tube 4 are circular, and the center position of both is O. Further, it is assumed that the slot antennas 51 to 58 are located at positions 51a to 58a projected from the center position O to the center line CL1.

  The microwave M enters the annular waveguide 3 from the introduction port 3a, propagates toward the terminal end 3b to the terminal E1, and part of the microwave M is reflected by the terminal E1. The microwave M propagating in the annular waveguide 3 radiates to the dielectric tube 4 through the slot antennas 51 to 58 and is introduced into the housing 2 through the dielectric tube 4. The microwave M becomes a surface wave, and the process gas in the housing 2 is ionized and dissociated by the surface wave energy to generate plasma. The surface wave propagates along the inner surface of the dielectric tube 4 and spreads over the entire inner surface of the dielectric tube 4. As a result, plasma is generated in a region corresponding to the inner surface of the dielectric tube 4. Using this plasma, plasma processing such as film formation, etching, and ashing is performed.

  This will be described with reference to FIG. FIG. 4 is a schematic diagram showing an elementary process of a chemical reaction occurring in the plasma P region. As shown in the drawing, the axial direction of the circular dielectric tube 4, that is, the direction orthogonal to the substrate to be processed S is defined as the Z direction. With reference to the upper end surface 4A of the dielectric tube 4, ht is the length of the tube of the dielectric tube 4, and hg is the distance between the upper end surface 4A and the material gas introduction position by the side gas introduction tube 7. , Hs is the distance between the upper end surface 4A and the substrate S to be processed. Moreover, the process gas introduction position by the upper surface gas introduction pipe 6 is the same height as the upper end surface 4A.

  When the microwave M is introduced into the housing through the dielectric tube 4, a large number of ions, electrons, and radicals are generated near the inner surface of the dielectric tube 4 due to the high plasma density. Ions and electrons receive the action of the surface wave SW propagating along the inner surface of the dielectric tube 4 and move in a direction parallel to the surface to be processed of the substrate S to be processed, as indicated by arrows. Accordingly, since charged particles having high kinetic energy are hardly incident on the target surface of the target substrate S, processing with very little plasma damage is possible. Radicals having no charge diffuse in the direction of the substrate to be processed S (Z direction), collide with material gas molecules, and cause various gas phase reactions such as decomposition, excitation, and recombination, and the generated molecules become thin films. And deposited on the surface of the substrate S to be processed.

The state during the plasma treatment will be described with reference to FIGS.
FIG. 5 is a graph qualitatively showing the plasma potential distribution in the Z direction, FIG. 6 is a graph qualitatively showing the atmospheric temperature distribution in the enclosure in the Z direction, and FIG. 7 is an electron immediately above the substrate S to be processed. It is a graph which shows a density distribution qualitatively.

  In FIG. 5, the plasma potential is high and constant in the region corresponding to the tube length ht of the dielectric tube 4, and drops rapidly when the lower end surface (position ht) of the dielectric tube 4 is exceeded. It becomes very low at (hs). Therefore, the surface of the substrate S to be processed hardly receives plasma damage.

  In FIG. 6, the ambient temperature in the housing is high near the lower end surface (position ht) of the dielectric tube 4, but decreases as it moves away from the lower end surface of the dielectric tube 4 in the Z direction, and the substrate position (hs). Then it gets lower. For this reason, the surface of the substrate to be processed S is not exposed to a high temperature, so that it is possible to prevent thermal damage of the device formed on the substrate to be processed S, deterioration of film quality, and the like.

  FIG. 7 is a graph showing the difference between the case (a) of the plasma processing of the present embodiment and the comparative example (b) regarding the electron density distribution immediately above the substrate. The arrow range on the horizontal axis in FIG. 7A represents the inner diameter of the dielectric tube 4. The comparative example is a case of plasma processing by a so-called planar SWP processing apparatus using a linear waveguide that propagates microwaves straight and a flat dielectric having an area of x × y. In FIG. 7B, the length of the dielectric plate in the extending direction of the waveguide is represented by x, and the length of the dielectric plate in the direction orthogonal to the extending direction is represented by y.

  In the graph of FIG. 7A, the change in the electron density is small at each point immediately above the substrate S to be processed. On the other hand, in the graph of FIG. 7B, the change in electron density is large at each point immediately above the substrate to be processed in both the x and y directions. When the change amounts Δρ1 and Δρ2 between the central portion and the peripheral portion of the substrate to be processed are compared, Δρ1 <Δρ2. That is, this embodiment can generate uniform plasma compared to the comparative example, and uniform plasma processing can be performed on the entire surface of the substrate to be processed.

Hereinafter, the dimensions of the annular waveguide 3 and the positional relationship between the slot antennas 51 to 58 will be described.
Referring to FIG. 3 again, the length L1 of the center line CL1 of the annular waveguide 3 is such that the wavelength of the microwave M propagating in the waveguide is λg and the range from 0.95λg to λg is a constant k. , And is set to an integer multiple of the constant k. Here, the constant k is a numerical value obtained experimentally. When n is a positive integer, a standing wave of the microwave M is formed in the annular waveguide 3 by setting L1 = n × k. By forming the standing wave, the microwave M having the same phase can be radiated strongly from a certain position of the annular waveguide 3 at all times.

  Next, the shape and arrangement of the slot antennas 51 to 58 will be described with reference to FIGS. 8 and 9 are views schematically showing the shape and arrangement of the slot antenna by developing the annular waveguide 3 described with reference to FIGS. As described above, the positions of the slot antennas 51 to 58 are represented by the positions 51a to 58a on the center line.

  In FIG. 8, the interval p1 between the slot antennas is set to an integer multiple of a constant k. The distance between the starting point A and the slot antenna 51a adjacent thereto and the distance between the end point B and the slot antenna 58a adjacent thereto are both p2, and the distance p2 is expressed as L1 = For example, k or k / 2 is set so as to satisfy nxk. By setting in this way, the position of the slot antennas 51 to 58 can be matched with the phase of the standing wave of the microwave, and the microwave power can be efficiently absorbed by the dielectric tube 4.

  Regarding the shape and dimensions of the slot antenna, if the ratio of the length R1 in the longitudinal direction of the slot antenna to the length R2 in the width direction is r (= R1 / R2), r is in the range of 2.5 to 60, and R2 is set in the range of 1.0 to 20.0 mm. By taking such a shape and size, the microwave radiation to the dielectric tube 4 becomes efficient. The inner dimension of the width of the annular waveguide 3 (the width of the bottom plate 3d) is about 109 mm.

  The angle formed by the longitudinal direction of the slot antenna 53 and the center line CL1 is θ, and the angle formed by the longitudinal direction of the adjacent slot antenna 54 and the center line CL1 is 180 ° −θ. The slot antennas 51 to 58 are alternately arranged at different angles. As described above, by arranging the slot antenna to be inclined with respect to the center line CL1, surface waves are propagated in a balanced manner in both the microwave propagation direction and the orthogonal direction on the inner surface of the dielectric tube 4, and uniform plasma is obtained. Can be generated.

  FIG. 9 shows an arrangement example of slot antennas different from that in FIG. In FIG. 9, a first slot antenna group (51 to 53) is disposed near the center of the annular waveguide 3. A second slot antenna group in which two rows of upper slot antenna groups (61 to 63) and lower slot antenna groups (64 to 66) are arranged above and below the first slot antenna group. Is arranged.

  In the first slot antenna group (51 to 53), the interval p1 between the slot antennas is set to an integer multiple of a constant k. Similarly, in the second slot antenna group having the same column, the interval p1 between the slot antennas is set to an integer multiple of a constant k. Also, the first slot antenna group and the second slot antenna group are shown as being shifted by k / 4 in the figure, but are set to be shifted by an integral multiple of k / 4. Furthermore, the distance p2 between the starting point A and the slot antenna 51a is set to, for example, k or k / 2 so as to satisfy L1 = n × k.

  By setting the position of the slot antenna as described above, the positions of all the slot antennas can be matched to the phase of the standing wave of the microwave M, and the microwave power can be efficiently absorbed by the dielectric tube 4. Can do. Further, in the case of FIG. 9, the surface wave is propagated in a balanced manner in both the microwave propagation direction and the orthogonal direction on the inner surface of the dielectric tube 4 as compared with the case of FIG. Can do.

  The shape and dimensions of the slot antenna in FIG. 9 are the same as those in FIG. Regarding the inclination angle, the slot antennas 51 to 53 and 61 to 66 can be arranged to be inclined with respect to the center line CL1. The angle at which the longitudinal direction of the slot antenna is inclined with respect to the center line CL1 is such that the angle θ is in the range of 60 to 120 ° in the first slot antenna group, and the angle φ is −5 to + 5 ° in the second slot antenna group. Set to range. In FIG. 9, only the slot antenna 63 is shown tilted by an angle φ. The second slot antenna group is arranged such that the distance m from the edge in the width direction of the inner surface of the annular waveguide 3 is within 30 mm.

  By arranging the slot antenna as shown in FIGS. 8 and 9, the peak position of the electric field strength of the standing wave of the microwave M coincides with the position of the slot antenna, and the microwave M is effectively radiated. . The phase of the standing wave slightly shifts as the microwave M propagates. However, the positional shift is corrected by making the distance b1 from the end point B to the end point E1 of the annular waveguide 3 variable. be able to.

FIG. 10 is a graph generally showing the electric field strength distribution of the standing wave of the microwave M in the waveguide, and the center line length is the distance from the start point A to the end point B.
In FIG. 10A, there is a positional shift s1 from the peak position of the standing wave at the position a1 of the slot antenna close to the starting point A, and the positional shift is caused by the propagation of the microwave M from the position a2 to a5. Is getting bigger. FIG. 10B shows a case where the end position is moved from E1 to E1 ′ by the end matching unit 3c so that the position shift s1 becomes zero. The position a1 of the slot antenna and the peak position of the standing wave coincide with each other, and the positional deviation hardly occurs in other slot antennas. That is, if the terminal position is adjusted, the microwave M is effectively radiated from each slot antenna.

<Second Embodiment>
FIG. 11 is an overall configuration diagram schematically showing a SWP processing apparatus according to the second embodiment of the present invention. FIG. 12 is a plan view showing the configuration of the microwave introduction unit of the SWP processing apparatus according to the second embodiment. 13 and 14 are views schematically showing the shape and arrangement of the slot antenna by developing the annular waveguide according to the second embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The SWP processing apparatus 200 of the present embodiment is greatly different from the SWP processing apparatus 100 of the first embodiment in the configuration of the annular waveguide.
Referring to FIGS. 11 and 12, the annular waveguide 30 includes a central waveguide 31 and slot waveguides 32 and 33 branched from the central waveguide 31. The slot waveguides 32 and 33 are disposed so as to contact and surround the outer surface of the dielectric tube 4. The slot waveguide 32 is provided with slot antennas 71 to 74, and a termination matching unit 32 c is provided at the termination portion 32 b of the slot waveguide 32. Similarly, the slot waveguide 33 is provided with slot antennas 75 to 78, and the termination matching unit 33 c is provided at the termination portion 33 b of the slot waveguide 33. In the present embodiment as well, as in the first embodiment, the positions (71a to 78a) of the slot antennas are represented with reference to the center lines CL2 and CL3 of the annular waveguide 30.

  In FIG. 12, the microwave M introduced from one end of the central waveguide 31 is separated into two at a branch point C on the center line, one of which proceeds to the slot antenna 71 side, along the center line CL2. And propagates to the end E2. The other travels toward the slot antenna 75 and propagates along the center line CL3 to the end E3. The center line length from the branch point C to the end point D is L2, and the center line length from the branch point C to the end point E is L3. The distance from the end point D to the end point E2 is b2, and the distance b2 is variable by the end matcher 32c. Similarly, the distance from the end point E to the end point E3 is b3, and the distance b3 is variable by the end matching unit 33c.

  By setting the center line lengths L2 and L3 of the slot waveguides 32 and 33 to L2 = n1 × k and L3 = n2 × k, the microwave M formed in the annular waveguide 30 is set. The positions 71a to 78a of the slot antennas 71 to 78 can be adjusted to the peak positions of the standing waves. As a result, the microwave M having the same phase can be efficiently radiated to the dielectric tube 4. As in the first embodiment, the constant k is a value in the range of 0.95λg to λg. N1 and n2 are positive integers.

  Since the annular waveguide 30 of this embodiment branches the microwave M into two and propagates the inside of the tube, the dimensions and the number of slot antennas are compared with the annular waveguide 3 of the first embodiment. Is the same, the deviation between the peak position of the standing wave and the position of the slot antenna can be further reduced. Further, since the annular waveguide 30 includes the two end matching units 32c and 33c, the position can be adjusted more accurately than the one end matching unit. Note that L2 and L3 may or may not be equal as long as the condition of an integral multiple of the constant k is satisfied.

  In the development of the annular waveguide 30 shown in FIGS. 13 and 14, the interval p1 between the slot antennas is set to an integer multiple of a constant k. In FIG. 13, the distances p2 from the branch point C of the slot antennas 71 and 75 adjacent to the branch point C are set so as to satisfy the conditions of L2 = n1 × k and L3 = n2 × k, respectively. Further, the slot antennas 71 to 78 are arranged such that the longitudinal direction thereof is orthogonal to the center lines CL2 and CL3.

  In FIG. 14, the slot antennas 81 to 88 are arranged such that the longitudinal direction thereof is at an angle θ or an angle of 180 ° −θ with respect to the center lines CL2 and CL3, the interval p1 between the slot antennas, and the slot antennas 71 and 75. The distance p2 from the branch point C is the same as in FIG.

  The present invention is characterized by a microwave introduction portion including an annular wave waveguide having a termination portion and a cylindrical dielectric member. The present invention is not limited to the embodiments described above as long as the characteristics are not impaired. For example, many variations of the arrangement of slot antennas are possible.

It is a whole lineblock diagram showing typically the SWP processing device concerning a 1st embodiment of the present invention. 1 is a schematic configuration diagram of a SWP processing device according to a first embodiment of the present invention. It is II sectional drawing of FIG. 2, and is a top view which shows the structure of a microwave introduction part. It is a schematic diagram which shows the elementary process of the chemical reaction which arises in the plasma production area | region in the SWP processing apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows qualitatively the plasma potential distribution of the Z direction in the SWP processing apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows qualitatively the atmospheric temperature distribution in the housing of the Z direction in the SWP processing apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows qualitatively the electron density distribution immediately above the to-be-processed substrate S in the SWP processing apparatus which concerns on the 1st Embodiment of this invention. It is an expanded view of the annular waveguide used for the SWP processing apparatus which concerns on the 1st Embodiment of this invention. It is another expanded view of the annular waveguide used for the SWP processing apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows generally the electric field strength distribution of the standing wave of the microwave in a waveguide. It is a whole block diagram which shows typically the SWP processing apparatus which concerns on the 2nd Embodiment of this invention. It is a top view which shows the structure of the microwave introduction part of the SWP processing apparatus which concerns on the 2nd Embodiment of this invention. It is an expanded view of the annular waveguide used for the SWP processing apparatus which concerns on the 2nd Embodiment of this invention. It is another expanded view of the annular waveguide used for the SWP processing apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Microwave generation part 2: Housing 3, 30: Annular waveguide 3a: Inlet 3b, 32b, 33b: Termination part 3c, 32c, 33c: Termination matching unit 4: Dielectric tube 5: Slot antenna 6: Upper surface Gas introduction pipe 7: Side gas introduction pipe 10: Microwave introduction section 100, 200: SWP treatment device A: Start point B, D, E: End point C: Branch points E1 to E3: End point M: Microwave

Claims (3)

An annular microwave waveguide having an inlet and a termination for introducing microwaves from the microwave generator, and having a bottom plate on which inner surfaces of a plurality of slot antennas are formed at predetermined intervals;
Cylindrical dielectric body that has a cylindrical shape, the outer side surface of which is in contact with the bottom plate of the annular microwave waveguide, and introduces microwaves propagating through the annular microwave waveguide through the slot antenna With members,
The length of the center line of the microwave waveguide surrounding the cylindrical dielectric member along the microwave propagation direction, where λg is the in-tube wavelength of the microwave and a constant k is in the range of 0.95λg to λg. Is set to an integer multiple of a constant k, and a predetermined interval between the plurality of slot antennas is set to an integer multiple of the constant k ,
The plurality of slot antennas include a first slot antenna group formed in the vicinity of the center of the bottom plate of the microwave waveguide and the vicinity of the periphery of the bottom plate of the microwave waveguide with reference to the center line of the microwave waveguide A second slot antenna group formed on
A microwave introduction device characterized in that the first slot antenna group and the second slot antenna group are arranged in parallel while being shifted in position by an integral multiple of k / 4 in the direction of the center line of the microwave waveguide. . In the microwave introduction device according to claim 1,
A microwave introducing device, wherein a termination matching unit is provided at a termination portion of the microwave waveguide. A microwave generator for generating microwaves;
  The microwave introduction device according to claim 1 or 2,
  An airtight space is formed by holding the cylindrical dielectric member, surface wave excited plasma is generated in the airtight space by microwaves introduced through the cylindrical dielectric member, and the surface wave excited plasma is used to generate the surface wave excited plasma. A surface wave excitation plasma processing apparatus comprising: a processing chamber for processing a processing object.

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