Plasma generating apparatus and plasma processing apparatus

Abstract

Provided is a microwave plasma generating apparatus using a multiple open-ended cavity resonator, and a plasma processing apparatus including the microwave plasma generating apparatus. The plasma processing apparatus includes a container for forming a process chamber, a support unit that supports a material to be processed in the process chamber, a dielectric window formed on an upper part of the process chamber, a gas supply unit that inject a process gas into the process chamber, and a microwave supply unit that includes a plurality of resonators for supplying microwaves through the dielectric window.

Description

BACKGROUND OF THE INVENTION

This application claims the priority of Korean Patent Application No. 2004-8174, filed on Feb. 7, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

1. Field of the Invention

The present invention relates to a semiconductor apparatus, and more particularly, to an apparatus for generating microwave plasma using a multiple open-ended cavity resonator and a plasma processing apparatus using the multiple open-ended cavity resonator.

2. Description of the Related Art

Plasma is ionized gas with no macroscopic electric charge due to an equal presence of positively charged ions and negatively charged electrons. Plasma is generated at a very high temperature and in a strong electric field or an RF electromagnetic field.

Plasma is generated by glow discharge when free electrons excited by a direct current (DC) or an RF electric field collide with gas molecules and generate active species such as ions, radicals, or electrons. Conventionally, a plasma process involves changing the characteristics of a material surface by physical and/or chemical interaction between the material surface and an obtained active species.

Currently, large area wafers are processed in the mass production of semiconductor devices. In order to perform a plasma process on a large-area wafer, a plasma processing apparatus must be able to accommodate the large-area wafer and generate plasma having uniform density. Such an apparatus is becoming increasingly important in semiconductor device production.

Among plasma generating apparatuses, research into plasma processing apparatuses using microwaves is currently in progress.

FIG. 1 is a cross-sectional view of a conventional plasma processing apparatus 10 using a bidirectional distributor.

The plasma processing apparatus 10 depicted in FIG. 1 is disclosed in U.S. Pat. No. 6,497,783, dated Dec. 24, 2002, and entitled “PLASMA PROCESSING APPARATUS PROVIDED WITH MICROWAVE APPLICATOR HAVING ANNUNLAR WAVEGUIDE AND PROCESSING METHOD”. The plasma processing apparatus 10 includes a container 11 for forming a processing chamber 19, a holding unit 12 that supports a wafer W loaded in the processing chamber 19, a heater 25 coupled under the holding unit 12, a gas supply unit 17 having a gas supply port 17a, a dielectric window 14 mounted on an upper part of the processing chamber 19 that isolates the processing chamber 19 from the outside atmosphere, and a microwave supply unit 13 formed on the dielectric window 14.

FIG. 2 is a perspective view of the microwave supply unit 13 of the conventional plasma processing apparatus 10 shown in FIG. 1.

Referring to FIGS. 1 and 2, the microwave supply unit 13 is a resonator formed of a conductive material, includes a space 13a through which microwaves propagate, upper and lower walls 13c and 13g, a plurality of slots 13b formed in the lower wall 13c adjacent to the dielectric window 14, a side wall 13d, a microwave introducing port 13e formed on the upper surface 13g, and a distributor 13f for introducing microwaves supplied from a waveguide 15 to the space 13a by dividing into two parts.

Referring to FIG. 1, the conventional plasma processing apparatus 10 includes a microwave power source 6 having a microwave oscillator such as a magnetron, at least two gas supply units, and a gas exhaust system. Each of the gas supply units includes a gas source 21, a valve 22, and a mass flow controller (MFC) 23. The gas exhaust system includes an exhaust control valve 26, a cut-off valve 25a, and a vacuum pump 24.

Plasma generation and processing in a conventional plasma processing apparatus 10 is performed as follows.

A wafer W is loaded onto a holding unit 12 and heated to a desired temperature. The processing chamber 19 is evacuated by the vacuum pump 24 and a plasma process gas flows into the process chamber 19 at a constant flow rate from the gas supply unit 17.

Next, power is applied to the microwave supply unit 13 from the microwave power source 6 via the waveguide 15. Microwaves supplied from the microwave supply unit 13 propagate into space 13a after being divided into two parts by the distributor 13f. The divided microwaves form standing waves by interfering with each other in space 13a.

The microwaves are strengthened at the plurality of slots 13b, and propagate into the process chamber 19 via the plurality of slots 13b and the dielectric window 14. An electric field of the microwaves supplied to the process chamber 19 accelerates electrons to generate high-density plasma at an upper part of the plasma process chamber 19. The processing gas in the process chamber 19 is then excited by the high density plasma to process a surface of the wafer W loaded on the holding unit 12.

FIGS. 3 a and 3b show a pattern of plasma formed by microwaves radiated from the plurality of slots 13b of the microwave supply unit 13, and a pattern of erosion corresponding to the slots 13b, respectively, when performing a deposition process using the conventional plasma processing apparatus 10.

Referring to FIGS. 3a and 3b, the conventional plasma processing apparatus 10 has an additional device having a plurality of slots A between a lower part of the microwave supply unit 13 and the dielectric window 14 to improve the density uniformity of plasma B. However, the additional device having the plurality of slots A causes erosion of the dielectric window 14 and consequent generation of unwanted particles. When performing a deposition of etching process using the conventional plasma processing apparatus, these unwanted particles, originating from erosion of the dielectric window 14, become impurities in a deposited or etched thin film.

SUMMARY OF THE INVENTION

The present invention provides a microwave plasma generating apparatus that can form a high-density and uniform plasma source in the vicinity of a material to be processed, and a plasma processing apparatus.

The present invention also provides a microwave plasma generating apparatus that can minimize power loss and avoid erosion of a dielectric window, and a plasma processing apparatus.

According to an aspect of the present invention, there is provided a plasma processing apparatus comprising a container for forming a process chamber, a support unit that supports a material to be processed in the process chamber, a dielectric window formed on an upper part of the process chamber, a gas supply unit that inject a process gas into the process chamber, and a microwave supply unit that includes a plurality of open ended cavity resonators for supplying microwaves through the dielectric window.

According to another aspect of the present invention, there is provided a microwave supply unit comprising a microwave power source for generating microwaves, a plurality of waveguides, a coupler for distributing the microwaves generated by the microwave power source to the plurality of waveguides, and a plurality of open ended cavity resonators.

According to another aspect of the present invention, when processing a material in a process chamber using a plasma processing apparatus having a microwave supply unit that includes a process chamber and a plurality of open-ended cavity resonators, uniform plasma density over the material can be maintained by individually controlling power supplied to the plurality of open-ended cavity resonators.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view illustrating a conventional plasma processing apparatus;

FIG. 2 is a perspective view of a microwave supply unit of the conventional plasma processing apparatus shown in FIG. 1;

FIGS. 3 a and 3b show a pattern of plasma formed by microwaves radiated from a plurality of slots of the microwave supply unit, and a pattern of erosion corresponding to the slots, respectively, when performing a deposition process using the conventional plasma processing apparatus shown in FIG. 1;

FIG. 4 is a cut-away perspective view of a plasma processing apparatus according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view of a microwave supply unit of the plasma processing apparatus of FIG. 4;

FIG. 6 is a graph of plasma density versus distance from a dielectric plate of the plasma processing apparatus of FIG. 4;

FIG. 7 is a schematic drawing illustrating a standing wave formed by a single resonator in a process chamber of the plasma processing apparatus of FIG. 4; and

FIG. 8 is a graph illustrating plasma density peaks generated by each of a plurality of resonators in the process chamber of the plasma processing apparatus of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. Like reference numerals refer to like elements throughout the drawings.

FIG. 4 is a cut-away perspective view illustrating a plasma processing apparatus according to an embodiment of the present invention.

As depicted in FIG. 4, a plasma processing apparatus 100 according to an embodiment of the present invention comprises a container 111 for forming a process chamber 109, a support unit 102 for supporting a substrate such as a wafer in the process chamber 109, a first gas supply unit 107 that includes a first gas inlet port 107a, a second gas supply unit 117 that includes a second gas inlet port 117a, a dielectric window 104 combined with an upper part of the process chamber 109 that separates the process chamber 109 from the outer atmosphere, and a microwave supply unit 130 formed on the dielectric window 104.

FIG. 5 is a cross-sectional view of the microwave supply unit 130 of the plasma processing apparatus 100 of FIG. 4.

The microwave supply unit 130 comprises a microwave power source 132, a coupler 134, an upper gas supply unit 108 that includes an upper gas inlet port 108a, a cooling water inlet port 136a, a cooling water outlet port 136b, first through n^th waveguides 103₁ through 103_n, and first through n^th resonators 113₁ through 113_n.

The microwave power source 132 of the microwave supply unit 130 includes a microwave generator such as a magnetron. The microwaves generated by the microwave power source 132 are supplied to the first through n^th resonators 113₁ through 113_n through each of the first through n^th waveguides 103₁ through 103_n by the coupler 134.

The first through n^th resonators 113₁ through 113_n according to the present invention, as parts of a multiple open-ended cavity resonator, have open-ends where they connect to the first through n^th waveguides 103₁ through 103_n and the dielectric window 104. Therefore, plasma distribution in the process chamber 109 can be made uniform by uniformly distributing microwaves over the entire surface of the dielectric window 104.

Referring to FIG. 4, in the plasma processing apparatus 100 according to an embodiment of the present invention, the upper gas supply unit 108 performs two functions. The first function is supplying cleaning gas for cleaning the process chamber 109 after depositing or etching a thin film on a substrate loaded on the support unit 102. For example, C₂F₆ gas may be supplied for cleaning the process chamber 109 after depositing a SiO₂ thin film. The other function is mechanically supporting a center portion of the dielectric window 104.

By mechanically supporting the center portion of the dielectric window 104, a large and relatively thin dielectric window 104 can be supported with reduced mechanical stress.

For uniform distribution of a process gas supplied to the substrate, a plasma source housing 107f includes the first gas supply unit 107 that includes the first gas inlet port 107a for injecting the process gas at a predetermined angle to a surface of the substrate. The second gas supply unit 117 including the second gas inlet port 117a is located under the plasma source housing 107f and is structured to provide a uniform distribution of gas flux in all azimuthally. Gas flux through each of the gas inlet ports described above can be controlled independently. Therefore, the distribution of the process gas supplied to the substrate can be made uniform.

A direct cooling system for cooling the dielectric window 104 is employed. That is, cooling water entering through the cooling water inlet port 136a directly contacts the dielectric window 104 and is discharged through the cooling water outlet port 136b to the outside after reducing a temperature gradient in the radial direction of the dielectric window 104.

The plasma processing apparatus 100 depicted in FIG. 4 uses a pair of co-axial type resonators, i.e., first and second resonators 113₁ and 113₂, for exciting the microwave plasma in the process chamber 109. The second resonator 113₂ is located near an edge of the dielectric window 104. The second resonator 113₂ is a bottom open-ended cavity resonator, and functions to generate very high-density plasma near the edge of the process chamber 109.

The microwave power generated by the microwave power source 132 enters the first and second waveguides 103₁ and 103₂ through the coupler 134. Each of the microwaves entering the first and second waveguides 103₁ and 103₂ enters each of the first and second resonators 113₁ and 113₂ via tapered waveguide units 105₁ and 105₂ connected to each of the waveguides 103₁ and 103₂.

An amount of microwave power generated by the microwave power source 132 and entering into the first and second resonators 113₁ and 113₂ can be controlled by first and second combining probes 112a and 112b included in the first and second waveguides 103₁ and 103₂.

Controlling the microwave entering into the first resonator 113₁ can control density of microwave plasma at the center portion of the process chamber 109. For example, changing a ratio of microwave power transmitted to the second waveguide 103₂ can control plasma uniformity in the radial direction in the process chamber 109.

The plasma processing apparatus 100 depicted in FIG. 4 uses a microwave plasma generating device composed of the first and second resonators 113₁ and 113₂. However, a plasma processing apparatus according to alternative embodiments of the present invention may use a microwave plasma generating device composed of any number of resonators.

In the case of a plasma processing apparatus according to an alternative embodiment of the present invention that uses a microwave plasma generating device employing n resonators, plasma uniformity in the vicinity of the dielectric window 104 in the process chamber 109 can be controlled by controlling a ratio of microwave power entering each of the resonators by controlling the coupler 134.

Also, although not shown, employing an individual microwave power source in each of the waveguides can control plasma uniformity.

The first and second movable flanges 115a and 115b are used for matching each of the waveguides to the corresponding microwave power sources.

Also, the first waveguide 103₁ can be rotated with respect to an axis of the process chamber 109, and the second waveguide 103₂ can be structured to rotate with respect to the first waveguide 113₁. Accordingly, the microwave plasma generating device can be easily combined with the plasma processing apparatus.

The support unit 102 is located under the process chamber 109 and can move up and down to place the substrate loaded on the support unit 102 at a level at which plasma uniformity is optimum.

According to the present invention, the plurality of microwave waveguides is co-axial and adjacent microwave waveguides share a wall.

FIG. 6 is a graph of plasma density versus distance from the dielectric window 104 toward a wafer substrate W mounted on the support unit 102 of the plasma processing apparatus of FIG. 4.

Referring to FIG. 6, d₂ represents optimum uniformity of plasma in the radial direction of the substrate W, and d₁ and d₃ represent less favorable plasma distributions. Since the wafer substrate W can be located at an optimum distribution region of plasma by adjusting a distance between the dielectric window 104 and the wafer substrate W, it is not necessary to create uniform plasma in the whole volume of process chamber 109 in order to get uniform flux on the substrate W. It is sufficient to control the individual plasma density peaks generated by the plurality of resonators 113₁ through 113_n in the process chamber 109.

FIG. 7 is a schematic drawing illustrating a standing wave formed by a single resonator in the process chamber 109.

Referring to FIG. 7, a standing wave has a peak at a location corresponding to a center line off the resonator. The amplitude of the standing wave indicates the magnitude of microwave power, and the plasma density in the process chamber 109 varies according to the microwave power.

FIG. 8 is a graph illustrating plasma density peaks generated by each of the plurality of resonators 113₁ through 113_n in the process chamber 109. For simplicity, the cooling water inlet port 136a and the cooling water outlet port 136b are omitted.

Referring to FIG. 8, a center peak 0 at the center of the process chamber 109 is formed by the first resonator 113₁. Peaks 0₂ through 0_n are formed at locations corresponding to center lines of the second through the nth resonators 113₂ through 113_n. Since all of the resonators are symmetrical with respect to the center of the process chamber 109, the peaks also have azimuthal symmetry. Accordingly, a top view of the peaks is a concentric circle.

The resonators are arranged to form the peaks 0₂-0_n at a predetermined distance from the center peak 0. Thus, as described above, the plasma density is varied according to distance from the dielectric window 104 in the process chamber 109, as depicted in FIG. 6. Therefore, according to the present invention, uniform plasma density in the radial direction at a predetermined distance from the dielectric window 104 can be obtained even if the plasma density is not uniform throughout the entire process chamber 109.

In order to form peaks at locations corresponding to the center lines of the resonators, resonance must occur in each of the resonators. A resonance condition of each of the resonators according to the present invention is that the perimeter of resonator center line must be equal to integer number of wavelengths of the microwave for waveguide corresponding to the resonator. At this time, it should be noted that, in the case of an open-type waveguide, the wavelength is not the same as in the case of a closed-type waveguide with conductive walls on all sides. This is because, in the open-type waveguide, not only a bent upper ring constituting the waveguide but also the dielectric window and the process chamber together form a resonator.

Even though an oscillation frequency in the resonator is determined by the frequency input from the microwave supply unit, the types of mode excited in each resonator also depend on location of coupling device. As far as the coupling occurs through a number of independent ports, each of input microwaves will excite its own resonance mode at same frequency.

Changing a ratio of microwave power transmitted to the corresponding resonator can control the amplitude of a peak at a given radial position. As depicted in FIG. 5, the microwave supply unit according to the present invention enables the use of three or more co-axial resonators at different radial distances from the center, and this is important for enabling uniform plasma processing over a large region.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

As described above, due to the structure of the plasma processing apparatus according to the present invention, plasma can be formed with a uniform distribution over a large substrate using a plurality of ring-type open-ended cavity resonators.

Also, erosion of a dielectric window can be avoided since the plasma processing apparatus according to the present invention does not use a plurality of slots for supplying microwaves through the dielectric window.

Also, a process gas can be ionized and decomposed effectively by supplying the process gas to locations close to the dielectric window.

Claims

1. A plasma processing apparatus comprising: a container for forming a process chamber; a support unit that supports a material to be processed in the process chamber; a dielectric window formed on an upper part of the process chamber; a gas supply unit that inject a process gas into the process chamber; and a microwave supply unit that includes a plurality of open ended cavity resonators for supplying microwaves through the dielectric window.

2. The plasma processing apparatus of claim 1, wherein the gas supply unit comprises: an upper gas supply unit mounted through the center of the dielectric window; a first gas supply unit for supplying the process gas to a surface of the material to be processed at a predetermined angle; and a second gas supply unit configured to have a radially uniform distribution of gas flux.

3. The plasma processing apparatus of claim 2, wherein gas flux through each of the gas supply units is independently controlled.

4. The plasma processing apparatus of claim 1, wherein the plurality of open-ended cavity resonators are open at portions contacting the dielectric window.

5. The plasma processing apparatus of claim 1, wherein the microwave supply unit comprises: a microwave power source for generating microwaves; a plurality of waveguides; a coupler for distributing the microwaves generated by the microwave power source to the plurality of waveguides; and a plurality of open ended cavity resonators connected to a plurality of waveguides, respectively.

6. The plasma processing apparatus of claim 5, wherein radial plasma uniformity in the process chamber can be improved by changing a ratio of microwave power transmitted to each of the waveguides.

7. The plasma processing apparatus of claim 5, wherein each of the waveguides are capable of rotation with respect to an axis of the process chamber.

8. The plasma processing apparatus of claim 5, wherein the plurality of waveguides are configured to be co-axial.

9. The plasma processing apparatus of claim 5, wherein adjacent waveguides share a common wall.

10. The plasma processing apparatus of claim 1, wherein the supporting means is able to move up and down to locate a substrate loaded on the supporting means at a level of optimum plasma uniformity.

11. A microwave supply unit comprising: a microwave power source for generating microwaves; a plurality of waveguides; a coupler for distributing the microwaves generated by the microwave power source to the plurality of waveguides; and a plurality of resonators.

12. The microwave supply unit of claim 11, wherein the coupler adjusts a ratio of microwave power transmitted to each of the waveguides.

13. The microwave supply unit of claim 11, wherein the waveguides are capable of rotation with respect to each other.

14. The microwave supply unit of claim 11, wherein portions of the plurality of open-ended cavity resonators opposite to the waveguides are open.

15. The microwave supply unit of claim 11, wherein the plurality of waveguides are configured co-axially.

16. The microwave supply unit of claim 11, wherein adjacent waveguides share a common wall.