JPH0268900A - Microwave plasma source - Google Patents

Abstract

PURPOSE:To increase the uniformity of plasma density within a plasma chamber by setting the mode of microwave to a particular mode. CONSTITUTION:A cylindrical plasma chamber 1 made of nonmagnetic metal is provided with a microwave introducing window 1a and a treated gas inlet 1b on one end thereof, and a quartz plate 2 is mounted to the microwave introducing window 1a to seal the plasma chamber 1, and a waveguide 3 is connected to the part of the quartz plate 2. In this case, the mode of microwave within the plasma chamber 1 is set to TM21 mode. Thus, the electric field of the microwave is collected in 4 points within the plasma chamber 1, and the four electric field collected points are dispersed nearly uniform within the section crossing at a right angle to the axial direction (the advance direction of the microwave) of the plasma chamber. Hence, the uniformity of the plasma density within the plasma chamber 1 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a microwave plasma source that converts processing gas introduced into a plasma chamber into plasma by electric discharge caused by electron cyclotron resonance.

[Conventional technology]

In conventional microwave plasma sources, a waveguide is connected to a cylindrical plasma chamber into which a processing gas is introduced to guide microwaves into the plasma chamber, and a magnet is installed to direct the microwave electric field into the plasma chamber. Orthogonal resonant magnetic fields are applied to cause discharge by electron cyclotron resonance in the plasma chamber, thereby turning the processing gas into plasma.

In this case, the microwave mode in the plasma chamber has an electromagnetic field distribution as shown in FIG. 5(a) (the solid line indicates the electric field distribution and the broken line indicates the magnetic field distribution).
+ mode, or T E + + mode having an electromagnetic field distribution as shown in Figure 5 (the solid line indicates the electric field distribution and the broken line indicates the magnetic field distribution).

[Problem to be solved by the invention]

However, the microwave mode in the plasma chamber is T
When set to the M o + mode, the microwave electric field intensity is maximum at the center of the plasma chamber, and the electric field intensity is minimum near the tube wall of the plasma chamber. Therefore, the plasma density becomes high at the center of the plasma chamber, and the plasma density becomes low near the tube wall of the plasma chamber.

In addition, the microwave mode in the plasma chamber can be changed to TE.
, mode, the electric field intensity is maximum near the X point near the tube wall of the plasma chamber, and the electric field intensity is the lowest near the Y point near the tube wall of the plasma chamber. Therefore, the plasma density becomes high near the X point, and the plasma density becomes low near the Y point.

As mentioned above, when the microwave mode in the plasma chamber is set to TMoI mode or TE mode, the uniformity of the plasma density in the plasma chamber is poor, and for example, when using the above-mentioned microwave plasma source, teC
When VD processing is performed, there is a problem in that the processing uniformity of the sample surface is poor.

Therefore, it is an object of the present invention to provide a microwave plasma source that can increase the uniformity of plasma density within a plasma chamber.

[Means to solve the problem]

The microwave plasma source of the present invention connects a waveguide that guides microwaves into a plasma chamber into which a processing gas is introduced, and applies a resonant magnetic field orthogonal to the electric field of the microwaves into the plasma chamber. A microwave plasma source equipped with a magnet that generates discharge by electron cyclotron resonance in a plasma chamber to turn processing gas into plasma, characterized in that the microwave mode in the plasma chamber is set to TMzl mode.

[For production]

According to the configuration of the present invention, since the microwave mode in the plasma chamber is set to TM mode, the number of microwave electric field concentration points in the plasma chamber is four; is distributed approximately evenly within a cross section perpendicular to the axial direction of the plasma chamber (the direction in which the microwaves travel). As a result, the uniformity of plasma density within the plasma chamber can be improved.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 to 4. This microwave plasma source is shown in FIG.
(As shown in bl, a microwave introduction window 1a and a processing gas introduction port 1b are provided at one end of a cylindrical plasma chamber 1 made of non-magnetic metal, and a quartz plate 2 is attached to the microwave introduction window 1a. Seal the quartz plate 2
A waveguide 3 is connected to the portion. In addition, a magnet 4 for applying a resonant magnetic field consisting of a coil is placed in the plasma chamber 1.
is placed in a state of encirclement.

Further, the other end of the plasma chamber 1 is connected to a sample chamber 5. A holder 6 is installed in this sample chamber 5, and a sample 7 to be subjected to CVD, for example, is placed on this holder 6.

Note that the sample chamber 5 is also provided with a processing gas inlet 5a. Note that the exhaust is performed from the sample chamber 5 in the direction of arrow B.

In such a microwave plasma source, a processing gas is introduced into the plasma chamber 1 and the sample chamber 5 through the processing gas introduction ports 1b and 5a.

Furthermore, microwaves are introduced into the plasma chamber 1 through the four-wave tube 3, and a resonant magnetic field perpendicular to the electric field of the microwave is applied to the plasma chamber 1 by the magnet 4. A discharge occurs due to cyclotron resonance, and this discharge turns the processing gas in the plasma chamber 1 into plasma, and the sample chamber 5
to touch the surface of sample 7.

In this case, the microwave mode in the plasma chamber 1 is 7M2. It is set to be the mode. In this way, when the microwave mode is set, there are four locations where the electric field of the microwave is concentrated within the plasma chamber 1, and the four locations where the electric field is concentrated are located in the axial direction of the plasma chamber 1 (the direction in which the microwaves travel). ) will be distributed approximately evenly within the cross section perpendicular to ). As a result, the uniformity of plasma density within the plasma chamber 1 can be improved.

Here, the tMi field distribution in the plasma chamber 1 when the microwave mode is set to T M t + mode will be explained based on FIGS. 2 to 4.

When the microwave mode is 7M mode, in FIG. 2, the electric field strength E in the radius ρ direction of the plasma chamber 1 is
(ρ) is E(ρ)=−j·β,·A 1llll dJ, (ρ)/d t is shown by curve P2 in FIG. Note that the function J, (ρ) and the function dJ, (ρ
) /d t are expressed as in equations (3) and (4), respectively.

h-ok! (n+k)!・・・・・・(3) t ・−2φ ・exp(j β,,,I・Z)・・
...Represented by +11.

However, xo is J, 1. =0 solution. Also, A.

Z is a coefficient. Further, β is expressed by the following formula.

ω
is shown by the curve P1 in FIG. 2, and the function dt
2 ......(4) Also, at this time, the electromagnetic field distribution in the cross section perpendicular to the axial direction (progressing direction of the microwave) in the plasma chamber l (the solid line indicates the electric field distribution, and the broken line indicates the magnetic field distribution) ) is shown in Figure 3 (
The electric field distribution in the axial direction of the LL cross section of FIG. 3 (11) is shown in FIG. 3(b).

From these figures, it can be seen that in the plasma chamber 1, electric field concentration occurs every 90 degrees at 60% of the radius, and the four electric field concentration points at every 90 degrees are located within a cross section perpendicular to the axial direction of the plasma chamber 1. TM□
It can be seen that the mode is superior to the TMII mode and the TEa mode in terms of uniformity of plasma density.

Next, set the microwave mode to TM mode.

Radius a and axial length b of plasma chamber 1 for setting to TE□ mode and TM□ mode, respectively
The relationship is shown in Figure 4. In Figure 4, the curve Ql is T
The curve Q shows the relationship between the radius a and the length b in the M t + s mode and the curve Q, in the T M + + s mode and the T
The same relationship is shown in FF, o+s mode, and the curve Q is T
E, shows the same relationship in 3 modes, curve Q4 is TM21
The same relationship is shown in the □ mode, and the curve Q is T M + +
The same relationship is shown in the z mode and the T E s +□ mode, and the curve Q shows the same relationship in the T E + + x mode.

From FIG. 4, it is clear that in the TM mode, the radius a can be made larger with the same length b, and therefore a larger plasma current can be obtained, compared to the TE mode and the T E e + mode. .

Furthermore, in the conventional example, the magnetic field applied in the plasma chamber 1 by the magnet 4 is a so-called divergent magnetic field, which is maximum near the microwave introduction window 1a and decreases as it approaches the sample 7. For example, if the resonance magnetic field strength is 84, which satisfies the electron cyclotron resonance condition,
The magnetic field strength generated by the magnet 4 was set so as to obtain 5 Gauss. However, as is well known, the magnetic field strength generated by the magnet 4 made of a coil has non-uniformity in the radial direction. Therefore, in the embodiment, if the magnetic field strength generated by the magnet 4 is set so that a resonant magnetic field strength is obtained at a location where the electric field strength is concentrated within the plasma chamber 1, the plasma density can be further increased.

〔Effect of the invention〕

According to the microwave plasma source of the present invention, since the microwave mode in the plasma chamber is set to T M t I mode, the number of microwave electric field concentration points in the plasma chamber is four; The electric field concentration point is in the axial direction of the plasma chamber (the direction of microwave propagation)
It will be distributed approximately evenly within the cross section perpendicular to . As a result, the uniformity of plasma density within the plasma chamber can be improved.

[Brief explanation of the drawing]

FIG. 1 (al is a schematic vertical sectional view showing the configuration of an embodiment of the present invention, FIG. 1 (bl is also a schematic horizontal sectional view, FIG. 2 is a schematic horizontal sectional view)
The figure shows the function Jt (ρ) and the function CZ, (ρ)/
dt graph, Figure 3 fat and lbl are explanatory diagrams of the electromagnetic field distribution in the plasma chamber of the example, and Figure 4 is TM.
11 mode, TEO mode, and TM mode. A graph showing the relationship between the radius a and the axial length b of the plasma chamber for setting the mode. FIG. 5 is an explanation of the electromagnetic field distribution in the plasma chamber in the conventional example. It is a diagram. 1... Plasma chamber, 3... Waveguide, 4...
Magnet diagram - a (mm)

Claims (1)

[Scope of Claims] A waveguide that guides microwaves into a plasma chamber into which a processing gas is introduced is connected to the plasma chamber, and a resonant magnetic field is applied to the plasma chamber to generate electron cyclotron resonance within the plasma chamber. TM_
A microwave plasma source characterized by being set to 2_1 mode.