JP4396166B2 - Surface wave excitation plasma processing equipment - Google Patents

Description

  The present invention relates to a surface wave excitation plasma processing apparatus for performing CVD, etching, and the like using surface wave plasma (SWP).

  In recent years, in a semiconductor manufacturing process, a plasma processing apparatus that performs each process using plasma for an etching process, a film forming process, an ashing process, or the like is used. As such a plasma processing apparatus, a parallel plate plasma processing apparatus, an ECR (Electron Cyclotron Resonance) plasma processing apparatus, and the like are conventionally used. Furthermore, in recent years, surface wave excitation (SWP) plasma processing apparatuses that can easily generate plasma with a larger area have been used (see, for example, Patent Document 1).

  In the SWP plasma processing apparatus, microwave power is supplied into the chamber from a slot antenna provided in the microwave waveguide through a dielectric provided on the chamber wall, and plasma is formed in the chamber. Since the microwave spreads the boundary between the dielectric and the plasma in the plane direction of the dielectric, it is easy to obtain a plasma with a large area.

JP 2000-348898 A

  However, when the width of the dielectric in the direction perpendicular to the extending direction of the waveguide is about 25 cm or more, a phenomenon that the plasma does not easily spread in the width direction is observed. In particular, when nitrogen gas, oxygen gas or other active gas species are used as the process gas, the tendency is remarkable. For this reason, it has been difficult to obtain a uniform plasma spread over the entire dielectric.

A surface wave excitation plasma processing apparatus according to a first aspect of the present invention is a dielectric for introducing a microwave into a plasma generating chamber, and a plurality of slot waveguides disposed on the dielectric and having a slot antenna. A microwave generating section for generating a microwave and three or more slot waveguides are connected in parallel, and the microwave from the microwave generating section is branched into three or more at a branch point, And the length from the branch point of the T-shaped branch waveguide to each end of each slot waveguide is set to an integral multiple of the in-tube wavelength of the microwave. It is characterized by.
According to a second aspect of the present invention, there is provided a surface wave-excited plasma processing apparatus comprising: (a) a plurality of dielectrics arranged in parallel on the outer wall of the plasma generation chamber; and (b) each of the plurality of dielectrics. A plasma source unit comprising a waveguide unit formed by connecting a plurality of slot waveguides having slot antennas in parallel by branching waveguides, and provided independently for each of the plurality of waveguide units, A branching waveguide having a plurality of microwave generators for sending microwaves to the branching waveguide and a surface wave reflector detachably provided in each gap between the plurality of dielectrics arranged in parallel. The length from the point to each end of the plurality of slot waveguides connected in parallel is set to an integral multiple of the in-tube wavelength of the microwave .
A third aspect of the present invention, the surface wave excited plasma processing apparatus according to claim 1 or 2, provided terminating matcher each to each end of the plurality of slots waveguide.

  According to the present invention, uniform plasma can be generated over the entire region of the dielectric, and a large-area substrate can be uniformly plasma-treated.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. 1 to 3 are schematic views for explaining a schematic configuration of a surface wave excitation plasma processing apparatus, FIG. 1 is a plan view of the apparatus, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. It is sectional drawing. The surface wave excitation plasma processing apparatus shown in FIGS. 1 to 3 constitutes a SWP-CVD apparatus for forming a SiNx film (silicon nitride film) or the like by SWP-CVD.

  Reference numeral 1 denotes a chamber in which a CVD process is performed. As shown in FIG. 2, a substrate 2 to be deposited is loaded in the chamber 1. Although not shown, the substrate 2 is held by a substrate holder or the like. A plasma source unit 3 is provided at a position facing the substrate 2 in the chamber 1. As shown in FIG. 1, a microwave generation unit 5 is connected to the plasma source unit 3 via a waveguide 4.

  The microwave generation unit 5 is provided with a microwave power source 50, a microwave oscillator 51, an isolator 52, a directional coupler 53, and a matching unit 54. When electric power is supplied from the microwave power source 50 to the microwave oscillator 51, a microwave of 2.45 GHz is output from the microwave oscillator 51. An isolator 52, a directional coupler 53, and a matching unit 54 are provided between the microwave oscillator 51 and the waveguide 4, and the microwave generated by the microwave oscillator 51 passes through these through the plasma source unit 3. Is sent out.

  As shown in FIG. 2, the plasma source unit 3 includes a waveguide unit 31 and a dielectric plate 32. Quartz, zirconia, or the like is used for the dielectric plate 32. FIG. 4 is a perspective view showing the external shape of the waveguide unit 31 disposed on the dielectric plate 32. The waveguide unit 31 includes a T-type branch waveguide 31a into which microwaves are introduced, and two slot waveguides 31b and 31c connected to the T-type branch waveguide 31a. The pair of slot waveguides 31 b and 31 c are arranged in parallel in the y direction of the dielectric plate 32, and each slot waveguide 31 b and 31 c extends along the x direction of the dielectric plate 32. . As shown in FIGS. 1 and 2, termination matching units 34 are provided at the ends of the slot waveguides 31b and 31c, respectively.

  The microwave introduced into the T-type branching waveguide 31a is branched into two by the T-type branching waveguide 31a, one of the branches is propagated to the slot waveguide 31b, and the other is the slot waveguide 31c. Propagate to. As shown in FIG. 3, the dielectric plate 32 is provided on the inner surface side of the upper wall 1 a, and the waveguide unit 31 is placed on the dielectric plate 32. A reflection plate 33 for reflecting microwaves is disposed around the dielectric plate 32. A slot antenna 300 for radiating a microwave toward the dielectric plate 32 is provided along the extending direction of the slot waveguides 31b and 31c on the bottom surface called the H-plane of each slot waveguide 31b and 31c. A plurality are formed at intervals (see FIGS. 2 and 3).

As shown in FIG. 2, when the SiNx film is formed by CVD, nitrogen gas (N ₂ ), hydrogen gas (H ₂ ), argon gas (Ar), and silane gas (SiH ₄ ) are supplied from the gas supply device 6 to the chamber. 1 is supplied. 61 is a supply source of nitrogen gas (N ₂ ), hydrogen gas (H ₂ ), and argon gas (Ar), and 62 is a supply source of silane gas (SiH ₄ ). During film formation, the pressure in the chamber 1 is maintained within the optimum pressure range for the film formation process by evacuating the chamber 1 from the exhaust port 1b while supplying a film forming gas.

  When microwaves radiated from the slot antenna 300 of the slot waveguides 31b and 31c are introduced into the chamber 1 through the dielectric plate 32, the gas in the chamber 1 is ionized and dissociated by the microwaves to generate plasma. Is done. When the electron density of the plasma exceeds the microwave cut-off density, the microwave becomes a surface wave and propagates along the boundary surface between the plasma and the dielectric plate 32 and spreads over the entire area of the dielectric plate 32.

The surface wave that has propagated to the periphery of the dielectric plate 32 is reflected by the reflecting plate 33 to form a standing wave. As a result, high-density plasma is formed over the entire region directly below the dielectric plate 32. The N ₂ gas, H ₂ gas, and Ar gas supplied from the gas supply device 6 are decomposed and excited by plasma to form radicals. SiH ₄ gas is decomposed and excited by these radicals, and Si and N are combined to form a silicon nitride film (SiNx film) on the substrate 2.

  Next, a method for setting the length dimension of the slot waveguides 31b and 31c will be described. Hereinafter, the wavelength of the microwave in the waveguide is represented by λg, and the branch point of the T-type branch waveguide 31a shown in FIG. In FIG. 4, the alternate long and short dash line indicates the center line of each of the waveguides 31a to 31c. For the slot waveguide 31b, the dimension from the branch point O to the end B of the slot waveguide 31b is an integral multiple of the wavelength λg. For the slot waveguide 31c, the dimension from the branch point O to the end C of the slot waveguide 31c is an integral multiple of the wavelength λg.

  Thus, by making the length of the slot waveguides 31b and 31c an integer multiple of the wavelength λg, the phase of the standing wave in all the slot waveguides 31b and 31c after the T-type branching waveguide 31a is obtained. Are equal. As a result, all the systems (slot waveguides 31b and 31c) can be matched with one matching unit 54 (see FIG. 1). In the example shown in FIG. 4, the lengths of the slot waveguides 31b and 31c in the x direction are equal, but may not be equal as long as the condition “integer multiple of wavelength λg” is satisfied.

  Each slot antenna 300 is arranged at a position where the intensity of the standing wave reaches a peak. For example, when five slot antennas 300a to 300e are provided in each of the slot waveguides 31b and 31c as shown in FIG. 4, the path lengths OE and OF from the branch point O to the slot antenna 300a closest to the branch point O are It is formed at a position that is an integral multiple of the wavelength λg. In this case, each of the pair of slot antennas 300a formed in the slot waveguides 31b and 31c is preferably set to an integral multiple of the wavelength λg so that the x positions are equal.

  The remaining slot antennas 300b to 300d are formed so that the interval between the slot antennas is λg. By arranging the slot antennas 300a to 300e in such a manner, the position where the intensity of the standing wave reaches a peak and the position of the slot antennas 300a to 300e coincide with each other, and microwave radiation is effectively performed. It should be noted that by adjusting the termination matching unit 34 provided at the end of each of the slot waveguides 31b and 31c, a slight positional deviation of the standing wave in each of the slot waveguides 31b and 31c is corrected. Can do.

  Further, the arrangement interval d of the slot waveguides 31b and 31c is set such that d = 30 cm when the y-direction dimension Dy of the dielectric is 60 cm as shown in FIG. With this arrangement, the electron density in the plasma has a distribution as shown in FIG. 5, and a uniform plasma spreading over the entire surface of the dielectric plate 32 can be formed. FIG. 6 qualitatively shows the electron density when only one slot waveguide is provided as in the prior art. As described above, the width in the y direction centered on the slot waveguide is as follows. If it exceeds 25 cm, the electron density decreases rapidly.

  When the size of the dielectric plate 32 is larger, the number of slot waveguides may be increased to 3 or more as in the waveguide unit 70 shown in FIG. FIG. 7 is a view similar to FIG. 4 and shows the waveguide unit 70 and the dielectric plate 32 constituting the plasma source section. In the waveguide unit 70 of FIG. 7, four slot waveguides 70b, 70c, 70d, and 70e are connected to one T-type branching waveguide 70a. Although not shown, a termination matching unit 34 is provided at the end of each slot waveguide 70b, 70c, 70d, 70e.

  Also in this case, the length of each of the slot waveguides 70b, 70c, 70d, 70e with respect to the branch point O is set to an integral multiple of the guide wavelength λg. In addition, the arrangement positions of the slot antennas 300 (not shown) formed in the slot waveguides 70b, 70c, 70d, and 70e are set by the same method as in the case of FIG.

  The example shown in FIG. 8 shows a case where plasma having a larger area is formed using four sets of waveguides and dielectric plates similar to those in FIG. The microwave generators 5 shown in FIG. 1 are independently connected to the four sets of waveguide units 71 to 74. In FIG. 8, one plasma source part is comprised by the waveguide units 71-74 and the four dielectric plates 32A-32D. Although not shown, a termination matching unit 34 is provided at each end of the slot waveguide provided in each of the waveguide units 71 to 74.

  Even when the four dielectric plates 32A to 32D are arranged in this manner, for example, the length of each slot waveguide of the waveguide unit 70 shown in FIG. It is also possible to adopt a configuration such that it is disposed on 32A to 32D. In this case, the microwave is sent from the single microwave generation unit 5 having a large capacity to each slot waveguide.

  However, as shown in FIG. 8, when generating plasma with a large area using the four dielectric plates 32A to 32D, it is necessary to supply a microwave power that is large enough to increase the plasma area. Therefore, it is possible to reduce the cost by using the general-purpose microwave power supply 50 configured as shown in FIG. 8 rather than manufacturing the high-power microwave power supply 50 exclusively.

  Further, when one microwave power source 50 is used, it is difficult to match the eight slot waveguides collectively with one matching unit 54 (see FIG. 1) as compared with the case of FIG. In the case of FIG. 8, since it is only necessary to independently match the four sets of waveguide units 71 to 74, the alignment can be adjusted more easily.

  In the apparatus of FIG. 8, it is also possible to perform plasma film formation using one to three sets of waveguides without using all of the four sets of waveguide units 71 to 74. For example, when only the waveguide unit 71 is used, the operations of the other waveguide units 72 to 74 are stopped to perform film formation. By doing so, it is possible to form a film by forming plasma having an area corresponding to the size of the substrate 2 (see FIG. 1).

  In that case, as shown in FIG. 9, a metallic reflector 75 may be detachably provided in the gap between the dielectric plates 32 </ b> A to 32 </ b> D. The surface wave propagating on the surface of the dielectric plate 32A in the left direction in the figure is reflected by the reflection plate 75 and does not spread to the adjacent dielectric plate 32B. As a result, plasma is formed in a space facing the dielectric plate 32A, and microwave energy is efficiently used. Further, when the waveguide unit 72 is also operated, the reflection plate 75 may be removed.

  The reflecting plate 75 can also be applied to the waveguide unit 31 as shown in FIG. That is, the dielectric plate 32 is divided into two between the slot waveguides 31b and 31c, and the reflection plate 75 is detachably provided in the divided gap portion. When only one slot waveguide is used, the entrance of the other waveguide may be blocked or the termination matching unit 34 may be adjusted so that no standing wave is formed.

  As described above, in the present invention, by providing the plurality of slot waveguides 31b and 31c connected by the T-shaped branch waveguide 31a on the dielectric plate 32, uniform plasma over the entire area of the dielectric plate 32 is generated. Can be formed. As a result, plasma processing, for example, plasma film formation can be performed uniformly over the entire area of the large-area substrate. In that case, the length of the slot waveguide with respect to the branch point of the T-shaped branch waveguide is set to an integral multiple of the in-tube wavelength λg of the microwave, and the slot antenna 300 is disposed as described with reference to FIG. Therefore, the plasma density can be made uniform.

  In the embodiment described above, the slot waveguides are arranged in parallel, but they need not be parallel. Further, the lengths of the slot waveguides may be different from each other as long as the condition of an integral multiple of the guide wavelength λg is satisfied. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

It is a top view which shows schematic structure of the surface wave excitation plasma processing apparatus by this invention. It is II-II sectional drawing of FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 1. It is a figure explaining the setting method of the length dimension of the slot waveguides 31b and 31c, and is a perspective view of the slot waveguides 31b and 31c and the dielectric plate 32. It is a figure which shows qualitatively the electron density distribution of the plasma at the time of using the slot waveguides 31b and 31c of FIG. It is a figure which shows qualitatively the electron density distribution of the plasma when only one lot waveguide is used. FIG. 5 is a perspective view showing a waveguide 70 in which four slot waveguides are connected in parallel. It is a perspective view which shows the plasma source part in the case of using 4 sets of a waveguide and a dielectric plate. It is sectional drawing which shows the plasma source part at the time of using the reflecting plate 75. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 2 Board | substrate 3 Plasma source part 4,31,70-74 Waveguide 5 Microwave generation part 6 Gas supply apparatus 31,70-74 Waveguide unit 31a, 70a T type branch waveguide 31b, 31c, 70a -70e Slot waveguide 32, 32A-32D Dielectric plate 34 Termination matching unit 33, 75 Reflector 300, 300a-300e Slot antenna O Branch point

Claims (3)

A dielectric for introducing microwaves into a chamber for generating plasma;
Three or more slot waveguides disposed on the dielectric and having slot antennas;
A microwave generator for generating microwaves;
The three or more slot waveguides are connected in parallel, and the microwaves from the microwave generation unit are branched into three or more at branch points and propagated to each of the slot waveguides. Prepared,
The surface wave excitation plasma processing apparatus characterized in that the length from the branch point of the T-shaped branch waveguide to each end of each slot waveguide is set to an integral multiple of the in-tube wavelength of the microwave. (A) a plurality of dielectrics arranged in parallel on the outer wall of the plasma generation chamber with a gap; and (b) a plurality of slot waveguides provided on each of the plurality of dielectrics and having a slot antenna. A plasma source unit comprising a waveguide unit connected in parallel by branching waveguides;
A plurality of microwave generators provided independently for each of the plurality of waveguide units, and for sending microwaves to the branch waveguide;
A surface wave reflector provided detachably in each gap between the plurality of dielectrics arranged side by side;
A surface wave excitation plasma characterized in that a length from a branch point of the branch waveguide to each end of the plurality of slot waveguides connected in parallel is set to an integral multiple of the in-tube wavelength of the microwave. Processing equipment. In the surface wave excitation plasma processing apparatus according to claim 1 or 2 ,
A surface wave excitation plasma processing apparatus, wherein a termination matching unit is provided at each end of the plurality of slot waveguides.

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