JP2004259581A - Plasma treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide plasma density suitable for a plasma treatment intended to be executed. <P>SOLUTION: This plasma treatment device is provided with a microwave guide tube 1 with a slot antenna 5 attached to its bottom face; a microwave introduction window 2 for forming a surface wave from the microwave introduced through the slot antenna 5 and transmitting it; an airtight vessel 10 for treating a treatment object by a surface wave-excited plasma; and closing reflectors 6 each having a reflecting surface R facing the outer peripheral side surface 2a of the introduction window 2. By moving the closing reflectors 6, the distance d between the reflecting surface R and the side surface 2a is adjusted. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma processing apparatus using surface wave excited plasma.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a semiconductor manufacturing process, a plasma technique is often used for film formation, etching processing, ashing processing, and the like. Plasma technology is also used for manufacturing solar cells, liquid crystal displays, plasma displays, and the like. If a high-density and uniform plasma is generated, an object to be processed can be stably and uniformly processed.
[0003]
As a plasma processing apparatus capable of generating high-density and uniform plasma, an apparatus using surface wave excited plasma (SWP) is known (for example, see Patent Document 1). This device introduces microwaves propagating in a waveguide from a slot antenna into a plasma generation chamber through a dielectric window (microwave introduction window), and a process gas in the plasma generation chamber is generated by surface waves generated on the surface of the dielectric window. To generate surface-wave-excited plasma. In the conventional plasma processing apparatus, the outer peripheral side surface of the dielectric window is surrounded by the inner wall of the airtight container.
[0004]
[Patent Document 1]
JP-A-2000-348898 (page 2, FIG. 1)
[0005]
[Problems to be solved by the invention]
In this type of plasma processing apparatus, the size of the surface wave excited plasma corresponds to the surface wave propagation region on the dielectric window. The inner dimensions of the hermetic container are one of the factors that determine the standing wave mode of the surface wave. A plasma density, a so-called discharge mode, is determined for each of the standing wave modes.
If the discharge mode changes when the microwave power or the gas pressure in the hermetic container is changed or the gas type is changed, there is a problem that a plasma density suitable for the plasma processing to be performed cannot be obtained. is there.
The present invention provides a plasma processing apparatus capable of obtaining a desired plasma density.
[0006]
[Means for Solving the Problems]
A plasma processing apparatus according to claim 1, wherein a microwave waveguide provided with a slot antenna on the bottom surface, a microwave introduction window for forming and propagating a surface wave from the microwave introduced through the slot antenna, and a process using the surface wave. It has an airtight container that generates a surface-wave-excited plasma by exciting gas and processes the object with the surface-wave-excited plasma, and has a reflective surface facing the outer peripheral side of the microwave introduction window. And a gap adjusting member for adjusting the gap between the window and the outer peripheral side face.
In the above-described plasma processing apparatus, the microwave introduction window has a rectangular shape, and the interval adjusting member is preferably capable of independently adjusting the intervals on four sides of the rectangular microwave introduction window.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a plasma processing apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram schematically showing a plasma processing apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the inside of the chamber of the plasma processing apparatus of FIG. 1 as viewed from below.
The plasma processing apparatus shown in FIGS. 1 and 2 includes a microwave waveguide 1, a dielectric plate 2, and a chamber 10 including a chamber body 3 and a flange 4. The chamber 10 is made of a non-magnetic metal material such as stainless steel, aluminum, and aluminum alloy.
[0008]
The microwave waveguide 1 is mounted on the upper surface of the dielectric plate 2. A plurality of slot antennas 5 for guiding microwaves to the dielectric plate 2 are formed on the bottom plate 1 a of the microwave waveguide 1.
The dielectric plate 2 is attached to the lower surface of the flange 4 so as to form an airtight space in the chamber 10. The dielectric plate 2 is made of a dielectric material such as quartz, alumina, zirconia, or Pyrex glass (registered trademark of Corning, USA).
[0009]
In FIG. 2, the closed reflectors 6a to 6d are attached to the lower surface of the flange 4 with bolts 7a to 7d so as to surround the dielectric plate 2. That is, the outer peripheral side surface 2a of the rectangular dielectric plate 2 is surrounded by the four closed reflectors 6a to 6d. The distance d between the reflection surface R of the closed reflectors 6a, 6b, 6c and 6d and the outer peripheral side surface 2a of the dielectric plate 2 is d1, d2, d3 and d4, respectively (in FIG. 1, it is represented as d). is there.
[0010]
The close reflectors 6a and 6b are provided with long holes 11a and 11b whose longitudinal direction is parallel to the left-right direction on the paper surface. The close reflectors 6a, 6b are attached to flanges (not shown) with bolts 7a, 7b penetrating the elongated holes 11a, 11b, respectively. The closed reflectors 6a and 6b can move with strokes corresponding to the lengths of the long holes 11a and 11b, respectively, and can change the distances d1 and d2.
Similarly, the closed reflectors 6c and 6d are provided with elongated holes 11c and 11d whose longitudinal direction is parallel to the vertical direction of the drawing. The closed reflectors 6c and 6d are attached to flanges (not shown) by bolts 7c and 7d that pass through the elongated holes 11c and 11d, respectively. The closed reflectors 6c and 6d can move with strokes corresponding to the lengths of the long holes 11c and 11d, respectively, and can change the intervals d3 and d4.
[0011]
To change the distance d, the bolt 7 may be loosened and the closed reflector 6 may be moved along the lower surface of the flange 4.
The closed reflector 6, like the chamber 10, is made of a non-magnetic metal material such as stainless steel, aluminum, or an aluminum alloy.
The close reflector 6 and the bolt 7 constitute a gap adjusting member.
[0012]
In FIG. 1, a chamber main body 3 is provided with a gas inlet 8 and a vacuum exhaust port 9. A process gas such as O ₂ , SiH ₄ , H ₂ , N ₂ , SF ₆ , Cl ₂ , Ar, and He is introduced from the gas inlet 8. By evacuating from the evacuation port 9 while introducing the process gas, the pressure in the chamber 10 is usually maintained at about 0.1 to 50 Pa.
[0013]
A microwave having a frequency of 2.45 GHz, for example, oscillated from a microwave output unit (not shown) travels inside the microwave waveguide 1 in a direction perpendicular to the plane of the drawing. The microwave passes through the slot antenna 5 and enters the dielectric plate 2, becomes a surface wave S, propagates on the surface of the dielectric plate 2 on the chamber body 3 side, and spreads instantaneously over the entire surface of the dielectric plate 2. . The propagation area of the surface wave S is substantially equal to the area of the surface of the dielectric plate 2.
The surface wave energy excites the process gas introduced into the chamber 10 to generate the plasma P. Although not shown, processing such as film formation, etching, and ashing is performed by placing an object to be processed in the plasma P.
[0014]
Next, the operation of the closed reflectors 6a to 6d will be described with reference to FIG.
The microwave M travels inside the microwave waveguide 1 from the bottom to the top of the page.
When the closed reflectors 6a to 6d are not present, the surface wave S maintains a standing wave mode determined by the inner dimensions of the chamber body 3. That is, the inner wall surface of the chamber main body 3 serves as a reflection surface, and the position of the reflection surface determines a unique standing wave mode. If the standing wave mode of the surface wave S is determined, the discharge mode (plasma density) of the plasma P excited by the surface wave S is also determined.
[0015]
Changing the distances d1 to d4 using the closed reflectors 6a to 6d according to the present embodiment corresponds to changing the inner dimensions of the chamber main body 3. By this operation, the standing wave mode of the surface wave S can be optimized, so that a desired plasma density can be obtained.
More specifically, by changing the distances d1 to d4, even when parameters such as microwave power and gas pressure are changed, or when the gas type is changed, the traveling wave of the surface wave S and the reflection from the close reflector 6 are changed. It is possible to prevent the waves from canceling each other.
[0016]
The distance d between the reflection surface R of the closed reflector 6 and the outer peripheral side surface 2a of the dielectric plate 2 is preferably in the range of 0 to λs / 2, where λs is the wavelength of the surface wave S. For example, in the TE01 mode, the guide wavelength λg of the microwave M is about 147 mm. Therefore, when quartz (dielectric constant ε = 3.6) is used as the dielectric plate, the wavelength of the microwave M propagating in the quartz plate is used. λ is about 77 mm. This is determined by λ = λg / ε ^1/2 . Assuming that λs ≒ λ, the standing wave mode of the surface wave S can be optimized if there is an adjustment range of λ / 2 = 38.5 mm.
[0017]
FIG. 3 is a modified example of the present embodiment, and is a partial plan view of the inside of the chamber of the plasma processing apparatus as viewed from below. FIG. 3A shows a case where the closed reflector 6d of FIG. 2 is divided into four parts to form closed reflectors 21 to 24. The distance d between the reflecting surfaces R of the closed reflectors 21 to 24 and the outer peripheral side surface 2a of the dielectric plate 2 is not constant but varies depending on the closed reflector. FIG. 3B shows a case where the closed reflector 6d is inclined at an angle θ with respect to the outer peripheral side surface 2a. Also in this case, the interval d is not constant.
As described above, by making the distance d variable depending on the location, the degree of freedom for adjustment for obtaining a desired plasma density is increased.
[0018]
Although a rectangular dielectric plate is used in the present embodiment, a circular dielectric plate may be used. In this case, the closed reflector has a cylindrical shape surrounding the dielectric disk. Changing the inner diameter of the cylindrical closed reflector changes the distance d. By preparing a plurality of cylindrical closed reflectors having different inner diameters and appropriately replacing them, it is possible to cope with not only a rectangular dielectric plate but also a circular dielectric plate.
[0019]
【The invention's effect】
As described above, according to the present invention, a plasma processing apparatus capable of obtaining a desired plasma density can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram schematically showing an entire plasma processing apparatus according to an embodiment of the present invention.
FIG. 2 is a plan view of the inside of the chamber of the plasma processing apparatus according to the embodiment of the present invention as viewed from below.
FIG. 3 is a modification of the embodiment of the present invention, and is a partial plan view of the inside of a chamber of the plasma processing apparatus as viewed from below.
[Explanation of symbols]
1: microwave waveguide 2: dielectric plate (microwave introduction window)
3: Chamber main body 4: Flange 5: Slot antenna 6: Closed reflector 10: Chamber M: Microwave S: Surface wave P: Plasma R: Reflection surface

Claims (2)

A microwave waveguide provided with a slot antenna on the bottom surface,
A microwave introduction window for forming and propagating a surface wave from the microwaves introduced through the slot antenna,
An airtight container that excites a process gas by the surface wave to generate a surface wave excited plasma, and processes an object to be processed by the surface wave excited plasma,
A plasma processing apparatus, comprising: a reflecting surface facing an outer peripheral side surface of the microwave introduction window; and an interval adjusting member for adjusting an interval between the reflecting surface and the outer peripheral side surface of the microwave introducing window. . The plasma processing apparatus according to claim 1,
The microwave introduction window has a rectangular shape,
The said gap adjustment member can adjust the said gap in four sides of the said rectangular microwave introduction window independently, The plasma processing apparatus characterized by the above-mentioned.

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